Lithographic printing plate precursor, lithographic printing method and packaged body of lithographic printing plate precursors

ABSTRACT

(1) A packaged body of lithographic printing plate precursors, wherein an image-recording layer or a protective layer of the outermost surface layer contains an inorganic layered compound. (2) A lithographic printing plate precursor having a protective layer containing an inorganic layered compound, and an image-recording layer containing a binder polymer. (3) A lithographic printing plate precursor having a protective layer containing an inorganic layered compound, and an image-recording layer containing an infrared absorber and an iodonium compound.

This application is a Divisional of co-pending U.S. application Ser. No.11/339,447 filed Jan. 26, 2006, which claims the benefit of priority ofJP 2005-018195, filed Jan. 26, 2005, JP 2005-022650, filed Jan. 31,2005, JP 2005-068924, filed Mar. 11, 2005, JP 2005-219200, filed Jul.28, 2005 and JP 2005-221594, filed Jul. 29, 2005. The entire content ofeach of the above-identified applications is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lithographic printing plate precursorand a packaged body of the lithographic printing plate precursors. Morespecifically, the invention relates to a lithographic printing plateprecursor capable of direct plate making by scanning with laser beams onthe basis of digital signals such as computer data, and a packaged bodyof the lithographic printing plate precursors.

2. Description of the Related Art

A lithographic printing plate generally comprises a lipophilic imagearea that receives ink and a hydrophilic non-image area that receives afountain solution in a printing process. Lithographic printing is aprinting method of making difference in ink-adhering property on thesurface of a lithographic printing plate with the lipophilic image areaof the lithographic printing plate as the ink-receptive area and thehydrophilic non-image area as the fountain solution receptive area(ink-repellent area) by making use of the natures of water and oily inkof repelling to each other, adhering ink only on the image area, andtransferring the ink to the material to be printed, e.g., paper.

For manufacturing the lithographic printing plate, a lithographicprinting plate precursor (a PS plate) comprising a hydrophilic supporthaving provided thereon a lipophilic photosensitive resin layer (animage-recording layer) has so far been widely used. The lithographicprinting plate is generally obtained by a plate-making method ofexposing a lithographic printing plate precursor through an originalimage of a lith film and the like, and then, for leaving the area tobecome an image area of the image-recording layer, dissolving andremoving other unnecessary image-recording layer with an alkalideveloping solution or an organic solvent, to thereby bare a hydrophilicsupport surface to form a non-image area.

In a conventional plate-making process of a lithographic printing plateprecursor, a process of dissolving and removing unnecessaryimage-recording layer with a developing solution and the like afterexposure is necessary, but the exclusion or simplification of such anadditional wet process is one of the objects in the industry. Since thediscard of waste solutions discharged with wet processes is aparticularly great interest in the industry at large in recent yearsfrom the consideration of the global environment, the solution of theabove problem is increasingly desired.

As a simple plate-making method, a method that is called on-pressdevelopment is proposed, which is a method of using an image-recordinglayer capable of removing an unnecessary area of a lithographic printingplate precursor in an ordinary printing process, and removing anon-image area after exposure on a printing press to obtain alithographic printing plate.

As the specific examples of on-press development, e.g., a method ofusing a lithographic printing plate precursor having an image-recordinglayer soluble or dispersible with, e.g., a fountain solution, an inksolvent, or an emulsified product of a fountain solution and ink, amethod of mechanically removing an image-recording layer by the contactwith the rollers and the blanket of a press, and a method ofmechanically removing an image-recording layer by the contact with therollers and the blanket after weakening the cohesive strength of animage-recording layer or the adhesive strength of an image-recordinglayer and a support by the permeation of a fountain solution and an inksolvent are exemplified.

In the present invention, unless otherwise indicated, “developmentprocess” means a process of removing an unexposed area of animage-recording layer of a lithographic printing plate precursor bybeing brought into contact with a liquid (generally an alkali developingsolution) to thereby bare the hydrophilic support surface with anapparatus other than a printing press (generally an automaticprocessor), and “on-press development” means a method and a process ofremoving an unexposed area of an image-recording layer of a lithographicprinting plate precursor by being brought into contact with a liquid(generally a printing ink and/or a fountain solution) to thereby barethe hydrophilic support surface with a printing press.

On the other hand, in recent years, digitized techniques ofelectronically processing image data, accumulating and outputting with acomputer have prevailed, and various image output systems correspondingto these digitized techniques have been put to practical use. Under suchcircumstances, a computer-to-plate technique directly making a printingplate is attracting public attention, which technique comprises scanningexposing a lithographic printing plate precursor with high convergentradiant rays such as laser beams carrying digitized image data withoutusing a lith film. With such a tendency, it is an important technicalsubject to obtain a lithographic printing plate precursor well adaptedto such a purpose.

Accordingly, in recent years, the simplification of plate-makingoperation, and the realization of dry system and non-processing systemhave been further strongly required from both aspects of theabove-described global environmental protection and the adaptation fordigitization.

To cope with this problem, there is disclosed in Japanese Patent No.2938397 a lithographic printing plate precursor comprising a hydrophilicsupport having provided thereon an image-forming layer containinghydrophobic thermoplastic polymer particles dispersed in a hydrophilicbinder. Japanese Patent No. 2938397 discloses that it is possible toperform on-press development with a fountain solution and/or ink bysubjecting the lithographic printing plate precursor to exposure withinfrared laser beams to coalesce the hydrophobic thermoplastic polymerparticles by heat to thereby form an image, and then mounting thelithographic printing plate precursor on the cylinder of a printingpress.

However, although a method of forming an image by coalescence of fineparticles by mere heat fusion as above certainly shows good on-pressdevelopability, there are problems that image strength is weak and presslife is insufficient.

Therefore, it is proposed to improve press life by making use ofpolymerization reaction. For example, a lithographic printing plateprecursor having an image-recording layer (a heat-sensitive layer)containing microcapsules encapsulating a polymerizable compound on ahydrophilic support is disclosed in JP-A-2001-277740 (The term “JP-A” asused herein refers to an “unexamined published Japanese patentapplication”.) JP-A-2002-287334 discloses a lithographic printing plateprecursor comprising a support having provided thereon animage-recording layer (a heat-sensitive layer) containing an infraredabsorber, a radical polymerization initiator and a polymerizablecompound. JP-A-2000-39711 discloses a lithographic printing plateprecursor capable of on-press development after exposure, whichlithographic printing plate precursor comprises an aluminum supportusing thereon a photosensitive composition containing (a) awater-soluble or water-dispersible polymer, (b) a monomer or an oligomerhaving a photopolymerizable ethylenic unsaturated double bond, and (c) aphoto-polymerization initiator having an absorption maximum in theultraviolet region. These methods using reactions such as polymerizationreaction are characterized in that the density of chemical bonding in animage area is high, so that image strength can be increased.

In general, as the preprocess of mounting a printing plate on a press onprinting site, the inspection and the discrimination of images on aprinting plate, i.e., works for ascertaining whether the images fittingfor the purpose are recorded on the printing plate or not, andascertaining for what a color of ink the plate is, are operated. Inordinary lithographic printing plate precursors accompanied by adevelopment process, an image can be easily ascertained after platemaking (after development process), or before printing (before aprinting plate is mounted on the press) generally by coloring animage-recording layer in advance.

However, since there is no image on a printing plate in a lithographicprinting plate precursor of an on-press development type or anon-processing (non-development) type not accompanied by developmentprocess before printing, the discrimination of a plate cannot be done,which sometimes leads to the error in operation. In particular inmulticolor printing, it is important for printing work to be capable ofdistinguishing whether register marks for register are clearly writtenso as to be distinguished or not.

To cope with this problem, there is disclosed in JP-A-11-277927 aphotosensitive lithographic printing plate containing a light-heatconverting agent having absorption in the wavelength region of 600 nm ormore, a compound capable of generating at least one selected from anacid, a base and a radical by light or heat, and a compound thatdiscolors by the interaction with at least one of the generated acid,base and radical. However, although the inspection work becomes easy byusing in an image-recording layer the combination of a leuco dyestuffwith a color developer or the combination of a light-acid generator witha pH indicator as the specific examples of the discoloring compounddisclosed in JP-A-11-277927, drawbacks arise such that paper lossincreases and printing performances are adversely influenced such thatsoiling resistance and press life are deteriorated, since a compoundthat does not concern image formation must be added for generatingdiscoloration.

Further, in a lithographic printing plate precursor having a radicalpolymerizable image-recording layer that is subjected to developmentprocessing, a protective layer is generally provided on theimage-recording layer for the purpose of polymerization acceleration(for achieving higher sensitivity and higher press life) by oxygenshielding, and prevention of the occurrence of scratches and ablationdue to high intensity laser exposure. A water-soluble polymeric compoundexcellent in crystallizability, e.g., polyvinyl alcohol, isconventionally used as the main component in such a protective layer.However, for sufficiently exhibiting the function, a relatively greatamount of a protective layer must be provided on the image-recordinglayer. Even if a great amount of a protective layer is provided on theimage-recording layer, the protective layer is all removed at the timeof development with a lithographic printing plate precursor accompaniedby development, so that there arises no problem in printing. However,with an on-press development type lithographic printing plate precursor,such a great amount of a protective layer causes the problems of delayof on-press development, mixing of removed substances in a fountainsolution, and accumulation on an impression drum, so that a protectivelayer capable of exhibiting the same function as conventional protectivelayers is required.

A lithographic printing plate precursor having a image-recording layercontaining a radical polymerization initiator, a polymerizable compoundand a polymer binder and further having provided thereon a protectivelayer is disclosed in U.S. Patent Application 2003/0,064,318A1. There isdisclosed in the same patent that a polymer having a polyethylene oxidesegment is used as the polymer binder, and the lithographic printingplate precursor is applicable to on-press development. However, sincethe prescription of the protective layer in U.S. Patent Application2003/0,064,318A1 is the same as those of conventionally used protectivelayers, when the coating solution of the protective layer is coated onthe image-recording layer, the image-recording layer partially dissolvesby the protective layer coating solution and the image-recording layerand the protective layer are mixed. Therefore, there is a problem inU.S. Patent Application 2003/0,064,318A1 that the image-forming propertyis rather hindered by coating the protective layer and sensitivity isreduced.

For preventing mechanical shock during preservation of lithographicprinting plate precursors, lithographic printing plate precursors aregenerally preserved and transported in the state that an interleaf isinserted between printing plate precursors. Interleaving sheets aregenerally manufactured from wood pulp, synthetic pulp (polyethylenefiber), natural fibers, e.g., hemp, reclaimed cellulose and the like.Interleaving sheets are necessary during preservation and transportationbut they are not necessary at all after lithographic printing plateprecursors are exposure processed, and generally they are recycled ordiscarded. With the increase of the consciousness of environmentalprotection in recent years, lithographic printing plate precursors thatdo not necessitate interleaving sheets are required in the printingindustry.

Lithographic printing plate precursors that do not necessitatedevelopment process and free from interleaving sheets are required asdescribed above. However, if polymerization reaction is applied tolithographic printing plate precursors that do not necessitatedevelopment process, the lithographic printing plate precursors areadhered to each other when they are laminated without using interleavingsheets, since the content of soft polymerizable compound accounting forin a photosensitive composition is high, and the image-recording layeror the protective layer is scratched, and aging stability and press lifeare deteriorated.

SUMMARY OF THE INVENTION

The invention intends to solve the above problems concerninglithographic printing plate precursors that do not necessitatedevelopment process. That is, an object of the invention is to provide apackaged body of lithographic printing plate precursors free ofinterleaving sheets not necessitating development process. Anotherobject of the invention is to provide a lithographic printing plateprecursor excellent in on-press developability and press life. A furtherobject of the invention is to provide an on-press development type or noprocessing type (non-development type) lithographic printing plateprecursor showing good visibility of a printing plate after exposure,generating little loss paper, and having good press life. A stillfurther object of the invention is to provide a lithographic printingmethod including on-press development of these lithographic printingplate precursors.

The present inventors have solved the above problems by the lithographicprinting plate precursor containing an inorganic layered compound in animage-recording layer or in a protective layer. That is the presentinvention is as follows.

(1) A packaged body of lithographic printing plate precursors, whichcomprises at least two lithographic printing plate precursors eachcomprising: a support; and an image-recording layer,

wherein a first one and a second one of the at least two lithographicprinting plate precursors are laminated so that a surface of a sidehaving an image-recording layer of the first one directly contacts witha surface of a side not having an image-recoeding layer of the secondone, and

wherein the image-recording layer comprises an inorganic layeredcompound.

(2) A packaged body of lithographic printing plate precursors, whichcomprises at least two lithographic printing plate precursors eachcomprising: a support; an image-recording layer; and a protective layerin this order,

wherein a first one and a second one of the at least two lithographicprinting plate precursors are laminated so that a surface of a sidehaving an image-recording layer of the first one directly contacts witha surface of a side not having an image-recoeding layer of the secondone, and

wherein the protective layer comprises an inorganic layered compound.

(3) A packaged body of lithographic printing plate precursors, whichcomprises at least two lithographic printing plate precursors eachcomprising: a support; an image-recording layer; and a protective layerin this order,

wherein a first one and a second one of the at least two lithographicprinting plate precursors are laminated so that a surface of a sidehaving an image-recording layer of the first one directly contacts witha surface of a side not having an image-recoeding layer of the secondone, and

wherein the at least two lithographic printing plate precursors each hasan outermost surface having a center line average surface roughness (Ra)of from 0.2 to 0.6 μm in a side having an image-recording layer.

(4) The packaged body of lithographic printing plate precursors asdescribed in any one of (1) to (3) above,

wherein the image-recording layer is capable of being removed by atleast one of a fountain solution and an ink.

(5) The packaged body of lithographic printing plate precursors asdescribed in any one of (1) to (4) above,

wherein the image-recording layer comprises (A) an actinic ray absorber,(B) a polymerization initiator and (C) a polymerizable compound.

(6) The packaged body of lithographic printing plate precursors asdescribed in any one of (1) to (5) above,

wherein the image-recording layer further comprises at least one ofmicrocapsules and microgels.

(7) A lithographic printing plate precursor comprising:

a support;

an image-recording layer comprising (A) an actinic ray absorber, (B) apolymerization initiator and (D) a binder polymer, and theimage-recording layer is capable of being removed by at least one of aprinting ink and a fountain solution; and

a protective layer comprising an inorganic layered compound, in thisorder,

wherein the binder polymer has an ethylene oxide group.

(8) The lithographic printing plate precursor as described in (7) above,

wherein the inorganic layered compound has an aspect ratio of 10 ormore.

(9) The lithographic printing plate precursor as described in (7) or (8)above,

wherein the binder polymer has from 2 to 120 repeating units comprisingan ethylene oxide group.

(10) The lithographic printing plate precursor as described in (7) or(8) above,

wherein the binder polymer has from 6 to 60 repeating units comprisingan ethylene oxide group.

(11) The lithographic printing plate precursor as described in any oneof (7) to (10) above,

wherein the binder polymer is water-insoluble.

(12) The lithographic printing plate precursor as described in any oneof (7) to (11) above,

wherein the image-recording layer comprises discontinuous particles.

(13) The lithographic printing plate precursor as described in any oneof (7) to (12) above,

wherein the binder polymer is polymer particles dispersed in theimage-recording layer.

(14) The lithographic printing plate precursor as described in any oneof (7) to (13) above,

wherein the image-recording layer comprises at least one ofmicrocapsules and microgels.

(15) The lithographic printing plate precursor as described in any oneof (7) to (14) above,

wherein the protective layer has a mass of from 0.02 to 1 g/m².

(16) A lithographic printing method comprising:

imagewise exposing a lithographic printing plate precursor as describedin any one of (7) to (15) above by irradiation with an actinic ray;

removing an area not irradiated with an actinic ray of theimage-recording layer by feeding at least one of a printing ink and afountain solution; and

performing printing.

(17) A lithographic printing plate precursor comprising:

a support;

an image-recording layer capable of imaging by an infrared laserexposure; and

a protective layer, in this order,

wherein the lithographic printing plate precursor is capable of printingby being mounted on a printing press without a development process afteran image recording or by an image recording after being mounted on aprinting press, and

wherein the image-recording layer comprises (E) an infrared absorber and(F) an iodonium salt and does not substantially comprise a compoundother than an infrared absorber (E) which changes a color of thecompound by interacting with at least one of an acid, a base and aradical, and the protective layer comprises an inorganic layeredcompound.

(18) The lithographic printing plate precursor as described in (17)above,

wherein an absorbance at any wavelength of from 400 to 700 nm of aninfrared absorber (E) in an exposed area changes by at least 0.05 ormore by an infrared laser exposure as compared with an absorbance of aninfrared absorber (E) in an unexposed area.

(19) The lithographic printing plate precursor as described in (17)above,

wherein an absorbance at any wavelength of from 400 to 700 nm of aninfrared absorber (E) in an exposed area becomes greater by at least0.05 or more by an infrared laser exposure as compared with anabsorbance of an infrared absorber (E) in an unexposed area.

(20) The lithographic printing plate precursor as described in any oneof (17) to (19) above,

wherein the infrared absorber (E) is a compound represented by formula(D1):

wherein R¹ and R² each independently represents a hydrogen atom or ahydrocarbon group having from 1 to 12 carbon atoms, and R¹ and R² may bebonded to each other to form a cyclic structure; Ar¹ and Ar² eachindependently represents an aromatic hydrocarbon group which may have asubstituent; Y¹ and Y² each independently represents a sulfur atom or adialkylmethylene group having 12 or less carbon atoms; R³ and R⁴ eachindependently represents a hydrocarbon group having 20 or less carbonatoms which may have a substituent; R⁵, R⁶, R⁷ and R⁸ each independentlyrepresents a hydrogen atom or a hydrocarbon group having 12 or lesscarbon atoms; R⁹ and R¹⁰ each independently represents an aromatichydrocarbon group having from 6 to 10 carbon atoms which may have asubstituent, an alkyl group having from 1 to 8 carbon atoms or ahydrogen atom, and R⁹ and R¹⁰ may be bonded to each other to form acyclic structure, and in this case, the cyclic structure may arbitrarilycontain one or more hetero atoms selected from the group consisting of anitrogen atom, an oxygen atom and a sulfur atom; and X⁻ represents acounter anion, provided that when any of R¹ to R⁸ is substituted with asulfo group, X⁻ is not necessary.

(21) The lithographic printing plate precursor as described in any oneof (17) to (20) above,

wherein the image recording layer further comprises a sulfonium salt.

(22) The lithographic printing plate precursor as described in any oneof (17) to (21) above,

wherein the image recording layer comprises at least one ofmicrocapsules and microgels.

(23) A lithographic printing method comprising:

imagewise exposing a lithographic printing plate precursor as describedin any one of (17) to (22) above with an infrared laser;

removing an unexposed area of an image-recording layer in a state offitting the lithographic printing plate precursor to a cylinder of aprinting press, so as to form a lithographic printing plate; and

performing printing with the lithographic printing plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a packaged body; and

FIG. 2 is a packaged body viewed diagonally.

DETAILED DESCRIPTION OF THE INVENTION 1. Packaged Body

The packaged body in the invention is the one packaging the laminate oflithographic printing plate precursors comprising a support havingprovided thereon an image-recording layer laminated in a manner that thesurface of the side having an image-recording layer of one lithographicprinting plate precursor and the surface of the side not having animage-recording layer of another lithographic printing plate precursorare directly brought into contact. The lithographic printing plateprecursors of the invention are shipped, transported and preserved inthis packaged form.

The number of lithographic printing plate precursors constituting onelaminate is not especially restricted, but in view of the efficienciesof transportation and preservation and the easiness of mounting on anautomatic plate making machine, for example, from 10 to 100 sheets arepreferred. In the case where a laminate is constituted of from 10 to 100sheets of lithographic printing plate precursors, it is preferred to fixthe protecting boards (attachment boards) used at the top surface andthe bottom surface of the laminate and the lithographic printing plateprecursors with a fixing means, e.g., an adhesive tape, so that thelithographic printing plate precursors do not get out of position fromeach other. A bundle of laminates may be constituted of severalthousands sheets of lithographic printing plate precursors. In the abovelaminate, a protecting board may be inserted every 20 to 100 sheets oflithographic printing plate precursors, or protecting boards may bearranged only at the top and bottom of the laminate. Protecting boardsmay be omitted in any of the above laminates.

The thus-constituted laminate is packaged with inner paper such asaluminum kraft paper, and then the folded parts of the inner paper arefixed with an adhesive tape, so that the inner paper does not carelesslyunfold or does not slip out, whereby a packaged body of lithographicprinting plate precursors is constituted. The packaged body may beencased in a shipping box for outer package or may be loaded onto apallet, according to necessity. For example, besides ordinary corrugatedboard box packaging, skid type package of packaging the laminates oflithographic printing plate precursors loaded onto a skid, and paperpallet type package of packaging the laminates loaded onto a paperpallet are exemplified. In the above package structure, inner paper maybe omitted.

2. Lithographic Printing Plate Precursor

The lithographic printing plate precursor in the invention comprises asupport having provided thereon an image-recording layer containing aninorganic layered compound, or comprises a support having animage-recording layer and a protective layer provided in this order andthe protective layer contains an inorganic layered compound. Inorganiclayered compound:

The inorganic layered compound for use in the invention comprises thintabular particles, e.g., a mica group such as natural mica and syntheticmica represented by the following formula, and talc represented byformula 3MgO.4SiO.H₂O, taeniolite, montmorillonite, saponite, hectorite,and zirconium phosphate are exemplified.

A(B,C)₂₋₅D₄O₁₀(OH, F,O)₂

wherein A is any of K, Na and Ca, B and C are any of Fe(II), Fe(III),Mn, Al, Mg and V, and D is Si or Al.

Out of the mica family, examples of the natural mica include muscovite,paragonite, phlogopite, biotite and lepidolite. Examples of thesynthetic mica include non-swelling mica such as fluorophlogopiteKMg₃(A1Si₃O₁₀)F₂ and potassium tetrasilicic mica, and swelling mica suchas Na-tetrasililic mica NaMg_(2.5)(Si₄O₁₀)F₂, Na- or Li-taeniolite (Na,Li)Mg₂Li(Si₄O₁₀)F₂, and montmorillonite-based Na- or Li-hectorite (Na,Li)_(1/8)Mg_(2/5)Li_(1/8)(Si₄O₁₀)F₂. Synthetic smectite is also useful.

In the present invention, among these inorganic layered compounds,fluorine-based swelling micas which are a synthetic inorganic layeredcompound are particularly useful. These swelling synthetic micas and theswelling clay minerals such as montmorillonite, saponite, hectorite andbentonite have a layered structure comprising unit crystalline latticelayers having a thickness of approximately from 10 to 15 Å, and theintra-lattice metallic atom substitution is considerably larger thanthat of other clay minerals. As a result, the lattice layer causesshortage in positive electric charge, and a cation such as Na⁺, Ca²⁺ andMg²⁺ is adsorbed between layers to compensate for the shortage. Thecation intervening between these layers is called an exchangeable cationand is exchanged with various cations. Particularly, in the case wherethe cation between layers is Li⁺ or Na⁺, the bonding between layeredcrystalline lattices is weak due to small ionic radius, and greatswelling with water occurs. When shearing is applied in this state,cleavage readily results and a stable sol is formed in water. Thistendency is outstanding in bentonite and swelling synthetic mica, andthese are useful in the present invention. In particular, swellingsynthetic mica is preferred.

As for the shape of the inorganic layered compound for use in thepresent invention, the thickness is preferably as small as possible fromthe standpoint of controlling the dispersion, and the plane size ispreferably as large as possible as long as the flatness of coatedsurface and the transparency to active light are not impaired.Therefore, the aspect ratio is 10 or more, preferably 20 or more, morepreferably 100 or more, still more preferably 200 or more. The aspectratio is a ratio of thickness to long diameter of a particle and can bemeasured, for example, from a projection view by a microphotograph ofparticles.

The particle size of the inorganic layered compound for use in thepresent invention is, in terms of average long diameter, from 0.3 to 20μm, preferably from 0.5 to 10 μm, more preferably from 1 to 5 μm. Theaverage thickness of the particle is 0.1 μm or less, preferably 0.05 μmor less, more preferably 0.01 μm or less. For example, out of inorganiclayered compounds, the swelling synthetic mica as a representativecompound has a size such that the thickness is from 1 to 50 nm and theplane size is approximately from 1 to 20 μm.

When such an inorganic layered compound particle having a large aspectratio is incorporated into the protective layer, the coating strength isincreased and the permeation of oxygen or water content can beeffectively inhibited, so that the protective layer can be preventedfrom deterioration due to deformation and even when stored for a longtime under high-humidity condition, the lithographic printing plateprecursor can be free of reduction in the image formability due tochange of humidity and exhibit excellent storage stability.

By using such an inorganic layered compound in an image-recording layeror a protective layer of the outermost surface layer of a lithographicprinting plate precursor, it becomes possible to prevent lithographicprinting plate precursors from being adhered to each other and beingscratched even when interleaving sheets are not used in a packaged bodyof lithographic printing plate precursors, so that excellent agingstability and press life can be maintained. The inorganic layeredcompounds used for a packaged body preferably have an aspect ratio of 20or more.

[Protective Layer]

In the present invention, the exposure is usually performed in air andthe protective layer prevents low molecular compounds such as oxygen andbasic substance present in air, which inhibit the image-forming reactionoccurring upon exposure in the image recording layer, from mingling intothe image recording layer and thereby prevents the inhibition ofimage-forming reaction at the exposure in air. Accordingly, the propertyrequired of the protective layer is low permeability to low molecularcompounds such as oxygen. Furthermore, the protective layer preferablyhas good transparency to light used for exposure, excellent adhesion tothe image recording layer, and easy removability during on-pressdevelopment after exposure. Various studies have been heretofore made onthe protective layer having such properties, and these are described indetail, for example, in U.S. Pat. No. 3,458,311 and JP-B-55-49729 (theterm “JP-B” as used herein means an “examined Japanese patentpublication”).

In the protective layer, a binder is preferably used together with theinorganic layered compound.

The binder is not particularly limited as long as the inorganic layeredparticle has good dispersibility therein and a uniform film adhering tothe image recording layer can be formed, and either a water-solublepolymer or a water-insoluble polymer may be appropriately selected andused. Specific examples of the binder include a water-soluble polymersuch as polyvinyl alcohol, modified polyvinyl alcohol,polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, partiallysaponified polyvinyl acetate, ethylene-vinyl alcohol copolymer,water-soluble cellulose derivative, gelatin, starch derivative and gumarabic, and a water-insoluble polymer such as polyvinylidene chloride,poly(meth)acrylonitrile, polysulfone, polyvinyl chloride, polyethylene,polycarbonate, polystyrene, polyamide and cellophane. These polymers mayalso be used in combination of two or more thereof, if desired.

Particularly, in view of easy removability of the protective layerremaining in the non-image area and handleability at the film formation,a water-soluble polymer is preferred and, for example, polyvinylalcohol, polyvinylpyrrolidone, polyvinylimidazole, water-soluble acrylicresin (e.g., polyacrylic acid), gelatin and gum arabic are preferred.Among these, polyvinyl alcohol, polyvinylpyrrolidone, gelatin and gumarabic are more preferred, because such a polymer can be coated by usingwater as the solvent and can be easily removed by a fountain solution atthe printing.

A part of the polyvinyl alcohol usable for the protective layer of thepresent invention may be replaced by an ester, an ether or an acetal ormay have another copolymerization component as long as the polyvinylalcohol contains an unsubstituted vinyl alcohol unit in a substantialamount for giving necessary water solubility. Examples of the polyvinylalcohol include those having a hydrolysis degree of 71 to 100 mol % anda polymerization degree of 300 to 2,400.

Specific examples thereof include PVA-105, PVA-110, PVA-117, PVA-117H,PVA-120, PVA-124, PVA-124H, PVA-CS, PVA-CST, PVA-HC, PVA-203, PVA-204,PVA-205, PVA-210, PVA-217, PVA-220, PVA-224, PVA-217EE, PVA-217E,PVA-220E, PVA-224E, PVA-405, PVA-420, PVA-613 and L-8 produced byKuraray Co., Ltd. Examples of the copolymer include chloroacetate orpropionate of polyvinyl acetate having a hydrolysis degree of 88 to 100mol %, polyvinyl formal, polyvinyl acetal, and a copolymer thereof.

In the lithographic printing plate precursors for use in the packagedbody of the invention, it is preferred that an inorganic layeredcompound to be added to an image-recording layer or a protective layerof the outermost surface layer is added in a range that the center lineaverage surface roughness (Ra) of the added layer becomes from 0.2 to0.6 μm.

The addition amount differs according to the inorganic layered compoundto be used, so that the specific addition amount cannot be determinedunconditionally, but when the compound is added to an image-recordinglayer, the amount is in general preferably from 1 to 50 mass % of allthe solids content in the image-recording layer, and more preferablyfrom 5 to 30 mass %. (In this specification, mass % and parts by massare equal to weight % and parts by weight, respectively.) When thecompound is added to a protective layer, the amount is preferably from 1to 70 mass % of all the solids content in the protective layer, and morepreferably from 10 to 50 mass %. In this range of the addition amount,adhesion of lithographic printing plate precursors to each other andscratching can be effectively prevented, and excellent aging stabilityand press life can be maintained.

The addition amount of the inorganic layered compound in thelithographic printing plate precursor as claimed in any of claims 7 to23 is preferably from 5/1 to 1/100 in mass ratio to the amount of thebinder used in the protective layer. When two or more kinds of inorganiclayered compounds are used in combination, it is preferred that thetotal amount of the inorganic layered compounds is also in the abovemass ratio.

A general dispersion method for the inorganic layered compound isdescribed below. From 5 to 10 parts by mass of the swelling layeredcompound described above as a preferred inorganic layered compound isadded to 100 parts by mass of water, thoroughly blended and swelled withwater, and then dispersed by a dispersing machine. Examples of thedispersing machine used here include various mills of dispersing thelayered compound by directly applying mechanical force, a high-speedagitation-type dispersing machine having large shearing force, and adispersing machine of giving highly intensified ultrasonic energy.Specific examples thereof include a ball mill, a sand grinder mill, avisco-mill, a colloid mill, a homogenizer, a dissolver, a polytron, ahomomixer, a homoblender, a KD mill, a jet agitator, a capillaryemulsifier, a liquid siren, an electromagnetic strain-type ultrasonicgenerator, and an emulsifier with Pullman's whistle. A dispersioncontaining from 5 to 10 mass % of the inorganic layered compounddispersed by the above-described method is in a highly viscous or gelledstate, and its storage stability is extremely good. At the time ofpreparing a protective layer coating solution by using this dispersion,the dispersion is preferably diluted with water, thoroughly stirred andblended with a binder solution.

In the protective layer coating solution, known additives such assurfactant for enhancing the coatability and water-soluble plasticizerfor improving the physical properties of film can be added in additionto the inorganic layered compound. Examples of the water-solubleplasticizer include propionamide, cyclohexanediol, glycerin andsorbitol. A water-soluble (meth)acrylic polymer may also be added.Furthermore, in this coating solution, known additives for enhancingadhesion to the image recording layer and aging stability of the coatingsolution may also be added.

The protective layer coating solution prepared in this way is coated onthe image recording layer provided on the support, and then dried toform a protective layer. The coating solvent may be appropriatelyselected according to the binder but when a water-soluble polymer isused, distilled water or purified water is preferably used as thesolvent. The coating method of the protective layer is not particularlylimited, and known methods such as method described in U.S. Pat. No.3,458,311 and JP-B-55-49729 may be applied. Specific examples of thecoating method for the protective layer include a blade coating method,an air knife coating method, a gravure coating method, a roll coatingmethod, a spray coating method, a dip coating method and a bar coatingmethod.

The coating weight of the protective layer is preferably in the range offrom 0.01 to 10 g/m² in dry coating weight, more preferably from 0.02 to3 g/m², and still more preferably from 0.02 to 1 g/m².

Image-Recording Layer (1):

The image-recording layer of the lithographic printing plate precursorfor use in the packaged body in the invention will be described in thefirst place. The image-recording layer is preferably a layer capable ofremoving by a printing ink and/or a fountain solution. Further, it ispreferred that the image-recording layer contains (A) an actinic rayabsorber, (B) a polymerization initiator, and (C) a polymerizablecompound.

When the image-recording layer is the outermost surface layer of thelithographic printing plate precursor, it contains an inorganic layeredcompound as described above.

The image-recording layer will be described in detail below.

(A) Actinic Ray Absorber:

Actinic ray absorbers for use in the invention are compounds that absorbthe rays radiated from an exposure light source, efficiently generateradicals from a polymerization initiator by a photon mode and/or a heatmode, to thereby contribute to the improvement of sensitivity of alithographic printing plate precursor. As such actinic ray absorbers,infrared absorbers are preferably used when a lithographic printingplate precursor is subjected to imagewise exposure with an infraredlaser, and sensitizing dyes absorbing lights of wavelengths of from 250to 420 nm are preferably used when a lithographic printing plateprecursor is imagewise exposed with an ultraviolet laser.

A1. Infrared Absorber:

The infrared absorbers for use in the invention are dyes or pigmentspreferably having an absorption maximum at the wavelengths of from 760to 1,200 nm.

As for the dye, commercially available dyes and known dyes described inpublications such as Senryo Binran (Handbook of Dyes), compiled by YukiGosei Kagaku Kyokai (1970) may be used. Specific examples thereofinclude dyes such as azo dye, metal complex salt azo dye, pyrazolone azodye, naphthoquinone dye, anthraquinone dye, phthalocyanine dye,carbonium dye, quinoneimine dye, methine dye, cyanine dye, squaryliumdye, pyrylium salt and metal thiolate complex.

Preferred examples of the dye include cyanine dyes described inJP-A-58-125246, JP-A-59-84356 and JP-A-60-78787, methine dyes describedin JP-A-58-173696, JP-A-58-181690 and JP-A-58-194595, naphthoquinonedyes described in JP-A-58-112793, JP-A-58-224793, JP-A-59-48187,JP-A-59-73996, JP-A-60-52940 and JP-A-60-63744, squarylium dyesdescribed in JP-A-58-112792, and cyanine dyes described in BritishPatent 434,875.

Also, a near infrared absorbing sensitizer described in U.S. Pat. No.5,156,938 may be suitably used. Furthermore, a substitutedarylbenzo(thio)pyrylium salt described in U.S. Pat. No. 3,881,924, atrimethinethiapyrylium salt described in JP-A-57-142645 (correspondingto U.S. Pat. No. 4,327,169), a pyrylium-based compound described inJP-A-58-181051, JP-A-58-220143, JP-A-59-41363, JP-A-59-84248,JP-59-84249, JP-A-59-146063 and JP-A-59-146061, a cyanine dye describedin JP-A-59-216146, a pentamethinethiapyrylium salt described in U.S.Pat. No. 4,283,475, and a pyrylium compound described in JP-B-5-13514and JP-B-5-19702 may also be preferably used. Other preferred examplesof the dye include near infrared absorbing dyes represented by formulae(I) and (II) of U.S. Pat. No. 4,756,993.

Among these dyes, preferred are a cyanine dye, a squarylium dye, apyrylium salt, a nickel thiolate complex and an indolenine cyanine dye,more preferred are a cyanine dye and an indolenine cyanine dye, stillmore preferred is a cyanine dye represented by the following formula(i):

In formula (i), X¹ represents a hydrogen atom, a halogen atom, —NPh₂,X²-L¹ or a group shown below:

wherein X² represents an oxygen atom, a nitrogen atom or a sulfur atom,L¹ represents a hydrocarbon group having from 1 to 12 carbon atoms, anaromatic ring having a heteroatom, or a hydrocarbon group having from 1to 12 carbon atoms and containing a heteroatom (the heteroatom as usedherein indicates N, S, O, a halogen atom or Se), X_(a) ⁻ has the samedefinition as Za⁻ described later, and R^(a) represents a substituentselected from a hydrogen atom, an alkyl group, an aryl group, asubstituted or unsubstituted amino group and a halogen atom. Phrepresents a phenyl group.

R¹ and R² each independently represents a hydrocarbon group having from1 to 12 carbon atoms. In view of storage stability of the coatingsolution for the recording layer, R¹ and R² each is preferably ahydrocarbon group having 2 to more carbon atoms, and R¹ and R² are morepreferably combined with each other to form a 5- or 6-membered ring.

Ar¹ and Ar² may be the same or different and each represents an aromatichydrocarbon group which may have a substituent. Preferred examples ofthe aromatic hydrocarbon group include a benzene ring and a naphthalenering, and preferred examples of the substituent include a hydrocarbongroup having 12 or less carbon atoms, a halogen atom and an alkoxy grouphaving 12 or less carbon atoms. Y¹ and Y² may be the same or differentand each represents a sulfur atom or a dialkylmethylene group having 12or less carbon atoms. R³ and R⁴ may be the same or different and eachrepresents a hydrocarbon group having 20 or less carbon atoms, which mayhave a substituent. Preferred examples of the substituent include analkoxy group having 12 or less carbon atoms, a carboxyl group and asulfo group. R⁵, R⁶, R⁷ and R⁸ may be the same or different and eachrepresents a hydrogen atom or a hydrocarbon group having 12 or lesscarbon atoms, and in view of availability of the raw material,preferably represents a hydrogen atom. Za⁻ represents a counter anion,but when the cyanine dye represented by formula (I) has an anionicsubstituent in its structure and neutralization of electric charge isnot necessary, Za⁻ is not present. In view of storage stability of thecoating solution for the recording layer, Za⁻ is preferably halogen ion,perchlorate ion, tetrafluoroborate ion, hexafluorophosphate ion orsulfonate ion, more preferably perchlorate ion, hexafluorophosphate ionor arylsulfonate ion.

Specific examples of the cyanine dye represented by formula (I), whichcan be suitably used in the present invention, include those describedin paragraphs [0017] to [0019] of JP-A-2001-133969.

Other preferred examples include a specific indolenine cyanine dyedescribed in JP-A-2002-278057.

Infrared absorbers are preferably water-soluble, but in the case of notwater-soluble, infrared absorbers can also be added as dispersion or bya method of dissolving them in a mixed solvent and the like.

As for the pigment used in the present invention, commercially availablepigments and pigments described in Color Index (C.I.) Binran (C.I.Handbook), Saishin Ganryo Binran (Handbook of Newest Pigments), compiledby Nippon Ganryo Gijutsu Kyokai (1977), Saishin Ganryo Oyo Gijutsu(Newest Pigment Application Technology), CMC Shuppan (1986), and InsatsuInk Gijutsu (Printing Ink Technology), CMC Shuppan (1984) can be used.

The kind of pigment includes a black pigment, a yellow pigment, anorange pigment, a brown pigment, a red pigment, a violet pigment, a bluepigment, a green pigment, a fluorescent pigment, a metal powder pigmentand a polymer bond pigment. Specific examples of the pigment which canbe used include an insoluble azo pigment, an azo lake pigment, acondensed azo pigment, a chelate azo pigment, a phthalocyanine-basedpigment, an anthraquinone-based pigment, a perylene- or perynone-basedpigment, a thioindigo-based pigment, a quinacridone-based pigment, adioxazine-based pigment, an isoindolinone-based pigment, aquinophthalone-based pigment, a dyed lake pigment, an azine pigment, anitroso pigment, a nitro pigment, a natural pigment, a fluorescentpigment, an inorganic pigment and carbon black. Among these pigments,carbon black is preferred.

These pigments may or may not be surface-treated before use. Examples ofthe method for surface treatment include a method of coating the surfacewith resin or wax, a method of attaching a surfactant, and a method ofbonding a reactive substance (for example, silane coupling agent, epoxycompound or isocyanate) to the pigment surface. These surface-treatingmethods are described in Kinzoku Sekken no Seishitsu to Oyo (Propertiesand Application of Metal Soap), Saiwai Shobo, Insatsu Ink Gijutsu(Printing Ink Technology), CMC Shuppan (1984), and Saishin Ganryo OyoGijutsu (Newest Pigment Application Technology), CMC Shuppan (1986).

The particle diameter of the pigment is preferably from 0.01 to 10 μm,more preferably from 0.05 to 1 μm, still more preferably from 0.1 to 1μm. Within this range, good stability of the pigment dispersion in thecoating solution for the image recording layer and good uniformity ofthe image recording layer can be obtained.

For dispersing the pigment, a known dispersion technique used in theproduction of ink or toner may be used. Examples of the dispersingmachine include an ultrasonic disperser, a sand mill, an attritor, apearl mill, a super-mill, a ball mill, an impeller, a disperser, a KDmill, a colloid mill, a dynatron, a three-roll mill and a pressurekneader. These are described in detail in Saishin Ganryo Oyo Gijutsu(Newest Pigment Application Technology), CMC Shuppan (1986).

The amount of the infrared absorbent added to the image recording layeris preferably a necessary minimum amount so as to suppress the sideeffect of inhibiting the polymerization reaction.

The infrared absorbent can be added at a ratio of 0.001 to 50 mass %,preferably from 0.005 to 30 mass %, more preferably from 0.01 to 10 mass%, based on the entire solid content of the image recording layer.Within this range, high sensitivity can be obtained without adverselyaffecting the uniformity or film strength of the image recording layer.

Of these infrared absorbers described above, a cyanine dye representedby formula (i) is preferred.

A2. Sensitizing Dye:

Sensitizing dyes for use in the invention are compounds havingabsorption at the wavelengths in the range of from 250 to 420 nm,specifically benzoin, benzoin methyl ether, benzoin ethyl ether,9-fluorenone, 2-chloro-9-fluorenone, 2-methyl-9-fluorenone, 9-anthrone,2-bromo-9-anthrone, 2-ethyl-9-anthrone, 9,10-anthraquinone,2-ethyl-9,10-anthraquinone, 2-t-butyl-9,10-anthraquinone,2,6-dichloro-9,10-anthraquinone, xanthone, 2-methylxanthone,2-methoxyxanthone, thioxanthone, benzyl, dibenzalacetone,p-(dimethylamino)phenyl styryl ketone, p-(dimethylamino)-phenyl,p-methyl styryl ketone, benzophenone, p-(dimethyl-amino)benzophenone (orMichler's ketone), p-(diethylamino)-benzophenone, and benzanthrone areexemplified.

Furthermore, preferred examples of the sensitizing dye for use in thepresent invention include a compound represented by formula (II)described in JP-B-51-48516:

wherein R¹⁴ represents an alkyl group (e.g., methyl, ethyl, propyl) or asubstituted alkyl group (e.g., 2-hydroxyethyl, 2-methoxyethyl,carboxymethyl, 2-carboxyethyl); R¹⁵ represents an alkyl group (e.g.,methyl, ethyl) or an aryl group (e.g., phenyl, p-hydroxyphenyl,naphthyl, thienyl); and

Z² represents a nonmetallic atom group necessary for forming anitrogen-containing heterocyclic nucleus usually used in a cyanine dye,for example, benzothiazoles (e.g., benzothiazole, 5-chlorobenzothiazole,6-chlorobenzothiazole), naphthothiazoles (e.g., α-naphthothiazole,β-naphthothiazole), benzoselenazoles (e.g., benzoselenazole,5-chlorobenzos elenazole, 6-methoxybenzoselenazole), naphthoselenazoles(e.g., α-naphthoselenazole, β-naphthoselenazole), benzoxazoles (e.g.,benzoxazole, 5-methylbenzoxazole, 5-phenylbenzoxazole) andnaphthoxazoles (e.g., α-naphthoxazole, β-naphthoxazole).

Specific examples of the compound represented by formula (II) includethose having a chemical structure constituted by combining these Z², R¹⁴and R¹⁵. Many of such compounds are present as a known substance andtherefore, the compound used may be appropriately selected from thoseknown substances. Other preferred examples of the sensitizing dye foruse in the present invention include a merocyanine dye described inJP-B-5-47095 and a ketocoumarin-based compound represented by thefollowing formula (iii):

wherein R¹⁶ represents an alkyl group such as methyl group and ethylgroup.

In addition, a merocyanine-based dye described in JP-A-2000-147763 canalso be used as the sensitizing dye, and a sensitizing dye described inJP-A-2001-100412 is also preferred. Specific examples thereof includethe following compounds.

The sensitizing dye can be added at a ratio of preferably from 0.1 to 50mass %, more preferably from 0.5 to 30 mass %, still more preferablyfrom 0.8 to 20 mass %, based on all solid contents constituting theimage recording layer.

(B) Polymerization Initiator:

The polymerization initiators that can be used in the invention arecompounds capable of generating radicals by light or heat, or both ofthese energies, and initiating and accelerating the polymerization of acompound having a polymerizable unsaturated group. As the polymerizationinitiators usable in the invention, well-known thermal polymerizationinitiators, compounds having a bond small in bonding and dissociationenergy, and photopolymerization initiators are exemplified.

As polymerization initiators as described above, e.g., organic halogencompounds, carbonyl compounds, organic peroxides, azo-basedpolymerization initiators, azide compounds, metallocene compounds,hexaarylbiimidazole compounds, organic boron compounds, disulfonecompounds, oxime ester compounds, oxime ether compounds and onium saltcompounds are exemplified.

Specific examples of the organohalogen compound include the compoundsdescribed in Wakabayashi et al., Bull. Chem. Soc. Japan, 42, 2924(1969), U.S. Pat. No. 3,905,815, JP-B-46-4605, JP-A-48-36281,JP-A-53-133428, JP-A-55-32070, JP-A-60-239736, JP-A-61-169835,JP-A-61-169837, JP-A-62-58241, JP-A-62-212401, JP-A-63-70243,JP-A-63-298339 and M. P. Hutt, Journal of Heterocyclic Chemistry, 1, No.3 (1970). Among these, an oxazole compound substituted with atrihalomethyl group, and an S-triazine compound are preferred.

Furthermore, an s-triazine derivative having at least one mono-, di- ortri-halogenated methyl group bonded to the s-triazine ring is morepreferred, and specific examples thereof include2,4,6-tris(monochloromethyl)-s-triazine,2,4,6-tris(dichloromethyl)-s-triazine,2,4,6-tris(trichloromethyl)-s-triazine,2-methyl-4,6-bis(trichloromethyl)-s-triazine,2-n-propyl-4,6-bis(trichloromethyl)-s-triazine,2-(α,α,β-trichloroethyl)-4,6-bis(trichloromethyl)-s-triazine,2-(3,4-epoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine,2-[1-(p-methoxyphenyl)-2,4-butadienyl]-4,6-bis(trichloromethyl)-s-triazine,2-styryl-4,6-bis(trichloromethyl)-s-triazine,2-(p-methoxystyryl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-1-propyloxy-styryl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine,2-(4-methoxynaphthyl)-4,6-bis(trichloromethyl)-s-triazine,2-phenylthio-4,6-bis(trichloromethyl)-s-triazine,2-benzylthio-4,6-bis(tri-chloromethyl)-s-triazine,2,4,6-tris(dibromomethyl)-s-triazine,2,4,6-tris(tribromomethyl)-s-triazine,2-methyl-4,6-bis(tribromomethyl)-s-triazine,2-methoxy-4,6-bis(tribromomethyl)-s-triazine and the followingcompounds.

Examples of the carbonyl compound include benzophenone derivatives suchas benzophenone, Michler's ketone, 2-methylbenzophenone,3-methylbenzophenone, 4-methylbenzophenone, 2-chlorobenzophenone,4-bromobenzophenone and 2-carboxybenzophenone; acetophenone derivativessuch as 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone,1-hydroxycyclohexylphenylketone, α-hydroxy-2-methylphenylpropanone,1-hydroxy-1-methylethyl-(p-isopropylphenyl)ketone,1-hydroxy-1-(p-dodecylphenyl)ketone,2-methyl-(4′-(methylthio)phenyl)-2-morpholino-1-propanone and1,1,1-trichloromethyl-(p-butylphenyl)ketone; thioxanthone derivativessuch as thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone,2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthoneand 2,4-diisopropylthioxanthone; and benzoic acid ester derivatives suchas ethyl p-dimethylaminobenzoate and ethyl p-diethylaminobenzoate.

Examples of the azo-based compound which can be used include azocompounds described in JP-A-8-108621.

Examples of the organoperoxide include trimethylcyclohexanone peroxide,acetylacetone peroxide,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane,1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)butane,tert-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzenehydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide,1,1,3,3-tetramethylbutyl hydroperoxide, tert-butylcumyl peroxide,dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane,2,5-oxanoyl peroxide, succinic peroxide, benzoyl peroxide,2,4-dichlorobenzoyl peroxide, diisopropylperoxy dicarbonate,di-2-ethylhexylperoxy dicarbonate, di-2-ethoxyethylperoxy dicarbonate,dimethoxyisopropylperoxy carbonate, di(3-methyl-3-methoxybutyl)peroxydicarbonate, tert-butylperoxy acetate, tert-butylperoxy pivalate,tert-butylperoxy neodecanoate, tert-butylperoxy octanoate,tert-butylperoxy laurate, tertiary carbonate,3,340,4,4′-tetra(tert-butylperoxycarbonyl)benzophenone,3,3′,4,4′-tetra(tert-hexylperoxycarbonyl)benzophenone,3,3′,4,4′-tetra(p-isopropyl-cumylperoxycarbonyl)benzophenone, carbonyldi(tert-butylperoxydihydrogendiphthalate) and carbonyldi(tert-hexylperoxydihydrogendiphthalate).

Examples of the metallocene compound include various titanocenecompounds described in JP-A-59-152396, JP-A-61-151197, JP-A-63-41484,JP-A-2-249, JP-A-2-4705 and JP-A-5-83588, such asdicyclopentadienyl-Ti-bis-phenyl,dicyclopentadienyl-Ti-bis-2,6-difluorophen-1-yl,dicyclopentadienyl-Ti-bis-2,4-difluorophen-1-yl,dicyclopentadienyl-Ti-bis-2,4,6-trifluorophen-1-yl,dicyclopentadienyl-Ti-bis-2,3,5,6-tetrafluorophen-1-yl,dicyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1-yl,dimethylcyclopentadienyl-Ti-bis-2,6-difluorophen-1-yl,dimethylcyclopentadienyl-Ti-bis-2,4,6-trifluorophen-1-yl,dimethylcyclopentadienyl-Ti-bis-2,3,5,6-tetrafluorophen-1-yl anddimethylcyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1-yl,bis(cyclopentadienyl)-bis(2,6-difluoro-3-(pyr-1-yl)phenyl)titanium andiron-allene complexes described in JP-A-1-304453 and JP-A-1-152109.

Examples of the hexaarylbiimidazole compound include various compoundsdescribed in JP-B-6-29285 and U.S. Pat. Nos. 3,479,185, 4,311,783 and4,622,286, such as2,2′-bis(o-chlorophenyl)-4,4′,5,5′-tetraphenylbiimidazole,2,2′-bis(o-bromophenyl)-4,4′,5,5′-tetraphenylbiimidazole,2,2′-bis(o,p-dichlorophenyl)-4,4′,5,5′-tetraphenylbiimidazole,2,2′-bis(o-chlorophenyl)-4,4′,5,5′-tetra(m-methoxyphenyl)biimidazole,2,2′-bis(o,o′-dichlorophenyl)-4,4′,5,5′-tetraphenylbiimidazole,2,2′-bis(o-nitrophenyl)-4,4′,5,5′-tetraphenylbiimidazole,2,2′-bis(o-methylphenyl)-4,4′,5,5′-tetraphenylbiimidazole and2,2′-bis(o-trifluorophenyl)-4,4′,5,5′-tetraphenylbiimidazole.

Examples of the organoboron compound include organoborates described inJP-A-62-143044, JP-A-62-150242, JP-A-9-188685, JP-A-9-188686,JP-A-9-188710, JP-A-2000-131837, JP-A-2002-107916, Japanese Patent2764769, JP-A-2002-116539, and Martin Kunz, Rad Tech '98. ProceedingApr. 19-22, 1998, Chicago; organoboron sulfonium complexes andorganoboron oxosulfonium complexes described in JP-A-6-157623,JP-A-6-175564 and JP-A-6-175561; organoboron iodonium complexesdescribed in JP-A-6-175554 and JP-A-6-175553; organoboron phosphoniumcomplexes described in JP-A-9-188710; and organoboron transition metalcoordination complexes described in JP-A-6-348011, JP-A-7-128785,JP-A-7-140589, JP-A-7-306527 and JP-A-7-292014.

Examples of the disulfone compound include compounds described inJP-A-61-166544 and JP-A-2003-328465.

Examples of the oxime ester compound include compounds described inJ.C.S. Perkin II, 1653-1660 (1979), J.C.S. Perkin II, 156-162 (1979),Journal of Photopolymer Science and Technology, 202-232 (1995),JP-A-2000-66385 and JP-A-2000-80068. Specific examples thereof includethe compounds represented by the following structural formulae.

As the above oxime ether compounds, the compounds disclosed inJP-A-8-202035 and JP-A-10-237118 are exemplified. Specifically, thecompounds represented by the structural formulae shown below can beexemplified.

Examples of the onium salt compound include onium salts such asdiazonium salts described in S. I. Schlesinger, Photogr. Sci. Eng., 18,387 (1974) and T. S. Bal et al., Polymer, 21, 423 (1980); ammonium saltsdescribed in U.S. Pat. No. 4,069,055 and JP-A-4-365049; phosphoniumsalts described in U.S. Pat. Nos. 4,069,055 and 4,069,056; iodoniumsalts described in European Patent 104,143, U.S. Pat. Nos. 339,049 and410,201, JP-A-2-150848 and JP-A-2-296514; sulfonium salts described inEuropean Patents 370,693, 390,214, 233,567, 297,443 and 297,442, U.S.Pat. Nos. 4,933,377, 161, 811, 410, 201, 339,049, 4,760,013, 4,734,444and 2,833,827, and German Patents 2,904,626, 3,604,580 and 3,604,581;selenonium salts described in J. V. Crivello et al., Macromolecules, 10(6), 1307 (1977) and J. V. Crivello et al., J. Polymer Sci., PolymerChem. Ed., 17, 1047 (1979); and arsonium salts described in C. S. Wen etal., Teh. Proc. Conf. Rad. Curing ASIA, page 478 (Tokyo, October 1988).

As preferred compounds in view of the reactivity and stability, theabove oxime ester compounds and onium salts (e.g., a diazonium salt, aniodonium salt, and a sulfonium salt) are exemplified. In the invention,these onium salts function as ionic radical polymerization initiatorsnot as acid generators.

The onium salt which is suitably used in the present invention is anonium salt represented by any one of the following formulae (RI-I) to(RI-III):

In formula (RI-I), Ar₁₁ represents an aryl group having 20 or lesscarbon atoms, which may have from 1 to 6 substituent(s), and preferredexamples of the substituent include an alkyl group having from 1 to 12carbon atoms, an alkenyl group having from 1 to 12 carbon atoms, analkynyl group having from 1 to 12 carbon atoms, an aryl group havingfrom 1 to 12 carbon atoms, an alkoxy group having from 1 to 12 carbonatoms, an aryloxy group having from 1 to 12 carbon atoms, a halogenatom, an alkylamino group having from 1 to 12 carbon atoms, adialkylamino group having from 1 to 12 carbon atoms, an alkylamido orarylamido group having from 1 to 12 carbon atoms, a carbonyl group, acarboxyl group, a cyano group, a sulfonyl group, a thioalkyl grouphaving from 1 to 12 carbon atoms, and a thioaryl group having from 1 to12 carbon atoms. Z₁₁ ⁻ represents a monovalent anion and specificexamples thereof include halogen ion, perchlorate ion,hexafluorophosphate ion, tetrafluoroborate ion, sulfonate ion, sulfinateion, thiosulfonate ion and sulfate ion. Among these, perchlorate ion,hexafluorophosphate ion, tetra-fluoroborate ion, sulfonate ion andsulfinate ion are preferred in view of stability.

In formula (RI-II), Ar₂₁ and Ar₂₂ each independently represents an arylgroup having 20 or less carbon atoms, which may have from 1 to 6substituent(s), and preferred examples of the substituent include analkyl group having from 1 to 12 carbon atoms, an alkenyl group havingfrom 1 to 12 carbon atoms, an alkynyl group having from 1 to 12 carbonatoms, an aryl group having from 1 to 12 carbon atoms, an alkoxy grouphaving from 1 to 12 carbon atoms, an aryloxy group having from 1 to 12carbon atoms, a halogen atom, an alkylamino group having from 1 to 12carbon atoms, a dialkylamino group having from 1 to 12 carbon atoms, analkylamido or arylamido group having from 1 to 12 carbon atoms, acarbonyl group, a carboxyl group, a cyano group, a sulfonyl group, athioalkyl group having from 1 to 12 carbon atoms, and a thioaryl grouphaving from 1 to 12 carbon atoms. Z₂₁ ⁻ represents a monovalent anionand specific examples thereof include halogen ion, perchlorate ion,hexafluorophosphate ion, tetrafluoroborate ion, sulfonate ion, sulfinateion, thiosulfonate ion and sulfate ion. Among these, perchlorate ion,hexafluorophosphate ion, tetrafluoroborate ion, sulfonate ion, sulfinateion and carboxylate ion are preferred in view of stability andreactivity.

In formula (RI-III), R₃₁, R₃₂ and R₃₃ each independently represents anaryl, alkyl, alkenyl or alkynyl group having 20 or less carbon atoms,which may have from 1 to 6 substituent(s), and in view of reactivity andstability, preferably represents an aryl group. Examples of thesubstituent include an alkyl group having from 1 to 12 carbon atoms, analkenyl group having from 1 to 12 carbon atoms, an alkynyl group havingfrom 1 to 12 carbon atoms, an aryl group having from 1 to 12 carbonatoms, an alkoxy group having from 1 to 12 carbon atoms, an aryloxygroup having from 1 to 12 carbon atoms, a halogen atom, an alkylaminogroup having from 1 to 12 carbon atoms, a dialkylamino group having from1 to 12 carbon atoms, an alkylamido or arylamido group having from 1 to12 carbon atoms, a carbonyl group, a carboxyl group, a cyano group, asulfonyl group, a thioalkyl group having from 1 to 12 carbon atoms, anda thioaryl group having from 1 to 12 carbon atoms. Z₃₁ ⁻ represents amonovalent anion and specific examples thereof include halogen ion,perchlorate ion, hexafluorophosphate ion, tetrafluoroborate ion,sulfonate ion, sulfinate ion, thiosulfonate ion and sulfate ion. Amongthese, perchlorate ion, hexafluorophosphate ion, tetrafluoroborate ion,sulfonate ion, sulfinate ion and carboxylate ion are preferred in viewof stability and reactivity. In particular, carboxylate ion described inJP-A-2001-343742 is more preferred, and carboxylate ion described inJP-A-2002-148790 is still more preferred.

Specific examples of the onium salt compound suitable for the presentinvention are set forth below, but the present invention is not limitedthereto.

The maximum absorption wavelength of the polymerization initiators foruse in the invention is preferably 400 nm or less, more preferably 360nm or less, and most preferably 300 nm or less. By bringing anabsorption wavelength into the ultraviolet region as above, the whitelight safety of a lithographic printing plate precursor is improved.

These polymerization initiators can be added in proportion of from 0.1to 50 mass % to the total solids content constituting an image-recordinglayer, more preferably from 0.5 to 30 mass %, and especially preferablyfrom 1 to 20 mass %. When the polymerization initiator is contained inthis range, good sensitivity and soiling resistance of a non-image areaat printing can be obtained. Polymerization initiators may be used onekind alone or two or more kinds may be used in combination.Polymerization initiators may be added with other components in the samelayer, or other layer may be provided for the addition of polymerizationinitiators.

<(C) Polymerizable Compound>

The polymerizable compound which can be used in the present invention isan addition-polymerizable compound having at least one ethylenicallyunsaturated double bond and is selected from compounds having at leastone, preferably two or more, ethylenically unsaturated bond(s). Suchcompounds are widely known in this industrial field and these knowncompounds can be used in the present invention without any particularlimitation.

These compounds have a chemical mode such as a monomer, a prepolymer(that is, dimer, trimer or oligomer) or a mixture or copolymer thereof.Examples of the monomer and its copolymer include an unsaturatedcarboxylic acid (e.g., acrylic acid, methacrylic acid, itaconic acid,crotonic acid, isocrotonic acid, maleic acid), and esters and amidesthereof. Among these, preferred are an ester of an unsaturatedcarboxylic acid with an aliphatic polyhydric alcohol compound, and anamide of an unsaturated carboxylic acid with an aliphatic polyvalentamine compound. Also, an addition reaction product of an unsaturatedcarboxylic acid ester or amide having a nucleophilic substituent such ashydroxyl group, amino group or mercapto group with a monofunctional orpolyfunctional isocyanate or epoxy, and a dehydrating condensationreaction product with a monofunctional or polyfunctional carboxylic acidmay be suitably used. Furthermore, an addition reaction product of anunsaturated carboxylic acid ester or amide having an electrophilicsubstituent such as isocyanate group or epoxy group with amonofunctional or polyfunctional alcohol, amine or thiol, and adisplacement reaction product of an unsaturated carboxylic acid ester oramide having a desorptive substituent such as halogen group or tosyloxygroup with a monofunctional or polyfunctional alcohol, amine or thiolmay also be suitably used. Other than these, compounds where theunsaturated carboxylic acid of the above-described compound is replacedby an unsaturated phosphonic acid, styrene, vinyl ether or the like, mayalso be used.

Specific examples of the ester monomer of an aliphatic polyhydricalcohol compound with an unsaturated carboxylic acid include thefollowings. Examples of the acrylic acid ester include ethylene glycoldiacrylate, triethylene glycol diacrylate, 1,3-butanediol diacrylate,tetramethylene glycol diacrylate, propylene glycol diacrylate, neopentylglycol diacrylate, trimethylolpropane triacrylate, trimethylolpropanetri(acryloyloxypropyl)ether, trimethylolethane triacrylate, hexanedioldiacrylate, 1,4-cyclohexanediol diacrylate, tetraethylene glycoldiacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, dipentaerythritol diacrylate,dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitoltetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate,tri(acryloyloxyethyl)isocyanurate, polyester acrylate oligomer andisocyanuric acid EO-modified triacrylate.

Examples of the methacrylic acid ester include tetramethylene glycoldimethacrylate, triethylene glycol dimethacrylate, neopentyl glycoldimethacrylate, trimethylolpropane trimethacrylate, trimethylolethanetrimethacrylate, ethylene glycol dimethacrylate, 1,3-butanedioldimethacrylate, hexanediol dimethacrylate, pentaerythritoldimethacrylate, pentaerythritol trimethacrylate, pentaerythritoltetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritolhexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate,b is [p-(3-methacryloxy-2-hydroxypropoxy)phenyl]dimethylmethane andbis[p-(methacryloxyethoxy)phenyl]dimethylmethane.

Examples of the itaconic acid ester include ethylene glycol diitaconate,propylene glycol diitaconate, 1,3-butanediol diitaconate, 1,4-butanedioldiitaconate, tetramethylene glycol diitaconate, pentaerythritoldiitaconate and sorbitol tetraitaconate. Examples of the crotonic acidester include ethylene glycol dicrotonate, tetramethylene glycoldicrotonate, pentaerythritol dicrotonate and sorbitol tetradicrotonate.Examples of the isocrotonic acid ester include ethylene glycoldiisocrotonate, pentaerythritol diisocrotonate and sorbitoltetraisocrotonate. Examples of the maleic acid ester include ethyleneglycol dimaleate, triethylene glycol dimaleate, pentaerythritoldimaleate and sorbitol tetramaleate.

Examples of other esters include aliphatic alcohol-based estersdescribed in JP-B-51-47334 and JP-A-57-196231, those having an aromaticskeleton described in JP-A-59-5240, JP-A-59-5241 and JP-A-2-226149, andthose containing an amino group described in JP-A-1-165613. These estermonomers may also be used as a mixture.

Specific examples of the amide monomer of an aliphatic polyvalent aminecompound with an unsaturated carboxylic acid includemethylenebisacrylamide, methylenebismethacrylamide,1,6-hexamethylenebisacrylamide, 1,6-hexamethyl enebismethacrylamide,diethylenetriaminetrisacrylamide, xylylenebisacrylamide andxylylenebismethacrylamide. Other preferred examples of the amide-typemonomer include those having a cyclohexylene structure described inJP-B-54-21726.

A urethane-based addition-polymerizable compound produced by using anaddition reaction of an isocyanate with a hydroxyl group is alsopreferred and specific examples thereof include a vinyl urethanecompound having two or more polymerizable vinyl groups within onemolecule described in JP-B-48-41708, which are obtained by adding avinyl monomer having a hydroxyl group represented by the followingformula (A) to a polyisocyanate compound having two or more isocyanategroups within one molecule:

CH₂═C(R₄)COOCH₂CH(R₅)OH  (A)

(wherein R₄ and R₅ each represents H or CH₃).

In addition, urethane acrylates described in JP-A-51-37193, JP-B-2-32293and JP-B-2-16765, and urethane compounds having an ethylene oxide-typeskeleton described in JP-B-58-49860, JP-B-56-17654, JP-B-62-39417 andJP-B-62-39418 are also suitably used. Furthermore, by usingaddition-polymerizable compounds having an amino or sulfide structurewithin the molecule described in JP-A-63-277653, JP-A-63-260909 andJP-A-1-105238, a photopolymerizable composition having very excellentphotosensitization speed can be obtained.

Other examples include a polyfunctional acrylate or methacrylate such aspolyester acrylates described in JP-A-48-64183, JP-B-49-43191 andJP-B-52-30490 and epoxy acrylates obtained by reacting an epoxy resinwith a (meth)acrylic acid. In addition, a specific unsaturated compounddescribed in JP-B-46-43946, JP-B-1-40337 and JP-B-1-40336, and a vinylphosphonic acid-based compound described in JP-A-2-25493 may be used.

In some cases, a structure containing a perfluoroalkyl group describedin JP-A-61-22048 is suitably used. Furthermore, those described as aphotocurable monomer or oligomer in Adhesion, Vol. 20, No. 7, pp.300-308 (1984) may also be used.

Details of the usage of these addition-polymerizable compounds, such asstructure, sole or combination use and amount added, can be freelyselected in accordance with the performance design of final lithographicprinting plate precursor and, for example, may be selected from thefollowing standpoints.

In view of sensitivity, a structure having a large unsaturated groupcontent per one molecule is preferred and in many cases, a bifunctionalor greater functional compound is preferred. For increasing the strengthof image area, namely, cured film, a trifunctional or greater functionalcompound is preferred. Also, a method of controlling both sensitivityand strength by using a combination of compounds differing in thefunctional number and in the polymerizable group (for example, anacrylic acid ester, a methacrylic acid ester, a styrene-based compoundor a vinyl ether-based compound) is effective.

The selection and usage of the addition-polymerizable compound areimportant factors also for the compatibility and dispersibility withother components (e.g., water-insoluble polymer, initiator, colorant) inthe image recording layer. For example, the compatibility may beimproved in some cases by using a low purity compound or using two ormore compounds in combination. Also, a specific structure may beselected for the purpose of enhancing the adhesion to the substrate,protective layer which is described later, or the like.

The above polymerizable compounds are used in a range of preferably from5 to 80 mass % in an image-recording layer, and more preferably from 25to 75 mass %. They may be used alone or two or more polymerizablecompounds may be used in combination. Proper structure, proportion andaddition amount of polymerizable compounds can be arbitrarily selectedin view of the degree of polymerization hindrance by oxygen, resolution,a fogging property, refractive index change, and surface stickiness, andlayer constitution and coating method such as under coating and topcoating can also be adopted.

Other components:

Besides the above components (A), (B) and (C), the image recording layerin the invention can contain, e.g., a binder polymer, a surfactant, acolorant, a printing out agent, a polymerization inhibitor (a thermalpolymerization preventive), a higher fatty acid derivative, aplasticizer, inorganic fine particles, and a low molecular weightcompound.

For the improvement of film properties and on-press developability ofthe image-recording layer, a binder polymer can be used in theinvention. Conventionally well-known binder polymers can be used with norestriction, and linear organic polymers having film properties arepreferably used. As the examples of such binder polymers, an acrylicresin, a polyvinyl acetal resin, a polyurethane resin, a polyurea resin,a polyimide resin, a polyamide resin, an epoxy resin, a methacrylicresin, a polystyrene resin, a novolak type phenolic resin, a polyesterresin, a synthetic rubber and a natural rubber are exemplified.

As more preferred binder polymers, (meth)acrylic resins, i.e., polymersof (meth)acrylic acid esters, are exemplified. Of such polymers,copolymers of alkyl (meth)acrylate and a monomer of a (meth)acrylic acidester in which the R moiety of —COOR has a —CH₂CH₂O— structure arepreferred. The specific examples thereof are shown below, but theinvention is not restricted thereto.

For heightening the film strength of image areas, it is preferred forbinder polymers to have a crosslinking property. For imparting acrosslinking property to binder polymers, it is effective to introduce acrosslinkable functional group such as an ethylenic unsaturated bondinto the main chain or side chain of binder polymers. A crosslinkablefunctional group may be introduced by copolymerization or by polymericreaction.

As the examples of polymers having an ethylenic unsaturated bond in themain chain of a molecule, poly-1,4-butadiene and poly-1,4-isoprene areexemplified.

As the examples of polymers having an ethylenic unsaturated bond in theside chain of a molecule, polymers of ester or amide of an acrylic acidor a methacrylic acid are exemplified, i.e., polymers in which at leasta part of the residue of the ester or amide (R of —COOR or CONHR) has anethylenic unsaturated bond.

The examples of residues having an ethylenic unsaturated bond (the aboveR) include —(CH₂)_(n)CR¹═CR²R³, —(CH₂O)_(n)CH₂CR¹═CR²R³,—(CH₂CH₂O)_(n)CH₂CR¹=CR²R³, —(CH₂)_(n)NH—CO—O—CH₂CR¹═CR²R³,—(CH₂)_(n)—O—CO—CR¹═CR²R³, and (CH₂CH₂O)₂—X (in the formulae, R¹, R² andR³ each represents a hydrogen atom, a halogen atom, an alkyl grouphaving from 1 to 20 carbon atoms, an aryl group, an alkoxyl group or anaryloxy group, and R¹ and R² or R³ may be bonded to each other to form aring, n represents an integer of from 1 to 10, and X represents adicyclopentadienyl residue).

The specific examples of ester residues include —CH₂CH═CH₂,—CH₂CH₂O—CH₂CH═CH₂, —CH₂C(CH₃)═CH₂, —CH₂CH═CH—C₆H₅,—CH₂CH₂OCOCH═CH—C₆H₅, —CH₂CH₂OCOC(CH₃)═CH₂, —CH₂CH₂OCOCH═CH₂,—CH₂CH₂—NHCOO—CH₂CH═CH₂, and —CH₂CH₂O—X (wherein X represents adicyclopentadienyl residue).

The specific examples of amide residues include —CH₂CH═CH₂, —CH₂CH₂—Y(wherein Y represents a cyclohexene residue), and —CH₂CH₂—OCO—CH═CH₂.

When free radicals (polymerization initiating radicals or the grownradicals of a polymerizable compound in the polymerization process) areadded to the crosslinkable functional groups of a binder polymer havinga crosslinking property, addition polymerization occurs directly betweenthe polymers or via the polymeric chains of the polymerizable compound,as a result, crosslinking is formed between the molecules of thepolymers, and the binder polymer is hardened. Alternatively, the atomsin the polymer (e.g., the hydrogen atoms on the carbon atoms contiguousto the crosslinkable functional groups) are extracted by free radicalsand polymer radicals are grown, and the polymer radicals are bonded toeach other, whereby crosslinking is formed between the polymermolecules, so that the binder polymer is hardened.

The content of crosslinkable groups in a binder polymer (the content ofradical polymerizable unsaturated double bonds by iodometry) ispreferably from 0.1 to 10.0 mmol per 1 g of the binder polymer, morepreferably from 1.0 to 7.0 mmol, and most preferably from 2.0 to 5.5mmol. When the content of crosslinkable groups is in this range, goodsensitivity and good aging stability can be obtained.

From the viewpoint of the improvement of the on-press developability ofan unexposed area of an image-recording layer, it is preferred thatbinder polymers have high solubility or dispersibility in ink and/or afountain solution.

For improving the solubility or dispersibility in ink, binder polymersare preferably lipophilic, and for improving the solubility ordispersibility in a fountain solution, binder polymers are preferablyhydrophilic. Accordingly, it is also effective in the invention to use alipophilic binder polymer and a hydrophilic binder polymer incombination.

As hydrophilic binder polymers, binder polymers having a hydrophilicgroup, e.g., a hydroxyl group, a carboxyl group, a carboxylate group, ahydroxyethyl group, a polyoxyethyl group, a hydroxypropyl group, apolyoxypropyl group, an amino group, an aminoethyl group, an aminopropylgroup, an ammonium group, an amido group, a carboxymethyl group, asulfonic acid group and a phosphoric acid group are preferablyexemplified.

The specific examples of hydrophilic binder polymers include gum arabic,casein, gelatin, starch derivative, carboxymethyl cellulose and thesodium salt thereof, cellulose acetate, sodium alginate, vinylacetate-maleic acid copolymers, styrene-maleic acid copolymers,polyacrylic acids and the salts thereof, polymethacrylic acids and thesalts thereof, homopolymers and copolymers of hydroxyethyl methacrylate,homopolymers and copolymers of hydroxyethyl acrylate, homopolymers andcopolymers of hydroxypropyl methacrylate, homopolymers and copolymers ofhydroxypropyl acrylate, homopolymers and copolymers of hydroxybutylmethacrylate, homopolymers and copolymers of hydroxybutyl acrylate,polyethylene glycols, hydroxypropylene polymers, polyvinyl alcohols,hydrolyzed polyvinyl acetate having a hydrolysis degree of 60 mol % ormore, preferably 80 mol % or more, polyvinyl formal, polyvinyl butyral,polyvinyl pyrrolidone, homopolymers and copolymers of acrylamide,homopolymers and copolymers of methacrylamide, homopolymers andcopolymers of N-methylolacrylamide, polyvinyl pyrrolidone,alcohol-soluble nylon, and polyether of 2,2-bis(4-hydroxy-phenyl)propaneand epichlorohydrin.

The binder polymers preferably have a mass average molecular weight ofpreferably 5,000 or higher, more preferably from 10,000 to 300,000, anda number average molecular weight of preferably 1,000 or higher, morepreferably from 2,000 to 250,000. The polydisperse degree (mass averagemolecular weight/number average molecular weight) is preferably from 1.1to 10.

The binder polymers may be any of random polymers, block polymers andgraft polymers, but random polymers are preferred.

These binder polymers can be synthesized according to conventionallywell-known methods. Binder polymers having a crosslinking group can beeasily synthesized according to radical polymerization or polymericreaction.

The binder polymers may be used alone or as a mixture of two or more.The content of the binder polymers is preferably from 10 to 90 mass % tothe total solids content of the image-recording layer, and morepreferably from 20 to 80 mass %. When the binder polymers are used inthis range, preferred strength of an image area and good image-formingproperty can be obtained.

It is preferred to use a polymerizable compound and the binder polymerin mass ratio of from 1/9 to 7/3.

In the invention, it is preferred to use a surfactant in animage-recording layer to accelerate the on-press developability at thetime of initiating printing and to improve the conditions of coatingsurface. As the surfactants for these purposes, nonionic surfactants,anionic surfactants, cationic surfactants, ampholytic surfactants andfluorine surfactants are used. Surfactants may be used alone or two ormore surfactants may be used in combination.

The nonionic surfactant for use in the present invention is notparticularly limited and a conventionally known nonionic surfactant canbe used. Examples thereof include polyoxyethylene alkyl ethers,polyoxyethylene alkylphenyl ethers, polyoxyethylene polystyrylphenylethers, polyoxyethylene polyoxypropylene alkyl ethers, glycerin fattyacid partial esters, sorbitan fatty acid partial esters, pentaerythritolfatty acid partial esters, propylene glycol monofatty acid esters,sucrose fatty acid partial esters, polyoxyethylene sorbitan fatty acidpartial esters, polyoxyethylene sorbitol fatty acid partial esters,polyethylene glycol fatty acid esters, polyglycerin fatty acid partialesters, polyoxyethylenated castor oils, polyoxyethylene glycerin fattyacid partial esters, fatty acid diethanolamides,N,N-bis-2-hydroxyalkylamines, a polyoxyethylene alkylamine, atriethanolamine fatty acid ester, a trialkylamine oxide, a polyethyleneglycol and a copolymer of polyethylene glycol and polypropylene glycol.

The anionic surfactant for use in the present invention is notparticularly limited and a conventionally known anionic surfactant canbe used. Examples thereof include fatty acid salts, abietates,hydroxyalkanesulfonates, alkanesulfonates, dialkylsulfosuccinic estersalts, linear alkylbenzenesulfonates, branched alkylbenzenesulfonates,alkyl naphthalenesulfonates,alkylphenoxypolyoxyethylenepropylsulfonates,polyoxyethylenealkylsulfophenyl ether salts, an N-methyl-N-oleyltaurinesodium salt, a monoamide disodium N-alkylsulfosuccinate, petroleumsulfonates, a sulfated beef tallow oil, sulfuric ester salts of fattyacid alkyl ester, alkylsulfuric ester salts, polyoxyethylene alkyl ethersulfuric ester salts, fatty acid monoglyceride sulfuric ester salts,polyoxyethylene alkylphenyl ether sulfuric ester salts, polyoxyethylenestyrylphenyl ether sulfuric ester salts, alkylphosphoric ester salts,polyoxyethylene alkyl ether phosphoric ester salts, polyoxyethylenealkylphenyl ether phosphoric ester salts, partially saponifiedstyrene/maleic anhydride copolymerization products, partially saponifiedolefin/maleic anhydride copolymerization products, andnaphthalenesulfonate formalin condensates.

The cationic surfactant for use in the present invention is notparticularly limited and a conventionally known cationic surfactant canbe used. Examples thereof include alkylamine salts, quaternary ammoniumsalts, polyoxyethylene alkylamine salts and polyethylene polyaminederivatives.

The amphoteric surfactant for use in the present invention is notparticularly limited and a conventionally known amphoteric surfactantcan be used. Examples thereof include carboxybetaines, aminocarboxylicacids, sulfobetaines, aminosulfuric esters and imidazolines.

The term “polyoxyethylene” in the above-described surfactants can beinstead read as “polyoxyalkylene” such as polyoxymethylene,polyoxypropylene and polyoxybutylene, and these surfactants can also beused in the present invention.

The surfactant is more preferably a fluorine-containing surfactantcontaining a perfluoroalkyl group within the molecule. Thisfluorine-containing surfactant includes an anionic type such asperfluoroalkylcarboxylate, perfluoroalkylsulfonate andperfluoroalkylphosphoric ester; an amphoteric type such asperfluoroalkylbetaine; a cationic type such asperfluoroalkyltrimethylammonium salt; and a nonionic type such asperfluoroalkylamine oxide, perfluoroalkyl ethylene oxide adduct,oligomer containing a perfluoroalkyl group and a hydrophilic group,oligomer containing a perfluoroalkyl group and a lipophilic group,oligomer containing a perfluoroalkyl group, a hydrophilic group and alipophilic group, and urethane containing a perfluoroalkyl group and alipophilic group. In addition, a fluorine-containing surfactantdescribed in JP-A-62-170950, JP-A-62-226143 and JP-A-60-168144 may alsobe suitably used.

The surfactants can be used individually or in combination of two ormore thereof.

The surfactant content is preferably from 0.001 to 10 mass %, morepreferably from 0.01 to 5 mass %, in the image-recording layer.

In the present invention, a dye having large absorption in the visiblelight region can be used as a colorant for the image. Specific examplesthereof include Oil Yellow #101, Oil Yellow #103, Oil Pink #312, OilGreen BG, Oil Blue BOS, Oil Blue #603, Oil Black BY, Oil Black BS, OilBlack T-505 (all produced by Orient Chemical Industry Co., Ltd.),Victoria Pure Blue, Crystal Violet (CI42555), Methyl Violet (CI42535),Ethyl Violet, Rhodamine B (CI145170B), Malachite Green (CI42000),Methylene Blue (CI52015), and a dye described in JP-A-62-293247. Also, apigment such as phthalocyanine-based pigment, azo-based pigment, carbonblack and titanium oxide may be suitably used.

The colorant is preferably added, because the image area and thenon-image area after image formation can be clearly distinguished. Theamount of the colorant added is preferably from 0.01 to 10 mass % in theimage-recording layer.

In the image-recording layer of the present invention, a compound ofundergoing discoloration by the effect of an acid or a radical can beadded so as to produce a print-out image. As such a compound, forexample, various dyes such as diphenylmethane-based,triphenylmethane-based, thiazine-based, oxazine-based, xanthene-based,anthraquinone-based, iminoquinone-based, azo-based and azomethine-baseddyes are effective.

Specific examples thereof include dyes such as Brilliant Green, EthylViolet, Methyl Green, Crystal Violet, Basic Fuchsine, Methyl Violet 2B,Quinaldine Red, Rose Bengale, Metanil Yellow, Thymolsulfophthalein,Xylenol Blue, Methyl Orange, Paramethyl Red, Congo Red, Benzopurpurine4B, α-Naphthyl Red, Nile Blue 2B, Nile Blue A, Methyl Violet, MalachiteGreen, Parafuchsine, Victoria Pure Blue BOH [produced by HodogayaChemical Co., Ltd.], Oil Blue #603 [produced by Orient Chemical IndustryCo., Ltd.], Oil Pink #312 [produced by Orient Chemical Industry Co.,Ltd.], Oil Red 5B [produced by Orient Chemical Industry Co., Ltd.], OilScarlet #308 [produced by Orient Chemical Industry Co., Ltd.], Oil RedOG [produced by Orient Chemical Industry Co., Ltd.], Oil Red RR[produced by Orient Chemical Industry Co., Ltd.], Oil Green #502[produced by Orient Chemical Industry Co., Ltd.], Spiron Red BEH Special[produced by Hodogaya Chemical Co., Ltd.], m-Cresol Purple, Cresol Red,Rhodamine B, Rhodamine 6G, Sulforhodamine B, Auramine,4-p-diethylaminophenyliminonaphthoquinone,2-carboxyanilino-4-p-diethylaminophenyliminonaphthoquinone,2-carboxystearylamino-4-p-N,N-bis(hydroxyethyl)aminophenyliminonaphthoquinone,1-phenyl-3-methyl-4-p-diethylaminophenylimino-5-pyrazolone and1-β-naphthyl-4-p-diethylaminophenylimino-5-pyrazolone, and leuco dyessuch as p,p′,p″-hexamethyltriaminotriphenyl methane (Leuco CrystalViolet) and Pergascript Blue SRB (produced by Ciba Geigy).

Other suitable examples include leuco dyes known as a material forheat-sensitive or pressure-sensitive paper. Specific examples thereofinclude Crystal Violet Lactone, Malachite Green Lactone, Benzoyl LeucoMethylene Blue,2-(N-phenyl-N-methylamino)-6-(N-p-tolyl-N-ethyl)aminofluorane,2-anilino-3-methyl-6-(N-ethyl-p-toluidino)fluorane,3,6-dimethoxyfluorane,3-(N,N-diethylamino)-5-methyl-7-(N,N-dibenzylamino)fluorane,3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluorane,3-(N,N-diethylamino)-6-methyl-7-anilinofluorane,3-(N,N-diethylamino)-6-methyl-7-xylidinofluorane,3-(N,N-diethylamino)-6-methyl-7-chlorofluorane,3-(N,N-diethylamino)-6-methoxy-7-aminofluorane,3-(N,N-diethylamino)-7-(4-chloroanilino)fluorane,3-(N,N-diethylamino)-7-chlorofluorane,3-(N,N-diethylamino)-7-benzylaminofluorane,3-(N,N-diethylamino)-7,8-benzofluorane,3-(N,N-dibutylamino)-6-methyl-7-anilinofluorane,3-(N,N-dibutylamino)-6-methyl-7-xylidinofluorane,3-piperidino-6-methyl-7-anilinofluorane,3-pyrrolidino-6-methyl-7-anilino fluorane,3,3-bis(1-ethyl-2-methylindol-3-yl)phthalide,3,3-bis(1-n-butyl-2-methylindol-3-yl)phthalide,3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-phthalide and3-(4-diethyl aminophenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide.

The dye of undergoing discoloration by the effect of an acid or aradical is preferably added in an amount of 0.01 to 10 mass % in theimage-recording layer.

In the image-recording layer of the present invention, a small amount ofa thermopolymerization inhibitor is preferably added so as to preventthe radical polymerizable compound from undergoing unnecessarythermopolymerization during the preparation or storage of theimage-recording layer.

Suitable examples of the thermopolymerization inhibitor includehydroquinone, p-methoxyphenol, di-tert-butyl-p-cresol, pyrogallol,tert-butyl catechol, benzoquinone,4,4′-thiobis(3-methyl-6-tert-butylphenol),2,2′-methylenebis(4-methyl-6-tert-butylphenol) andN-nitroso-N-phenylhydroxylamine aluminum salt.

The thermopolymerization inhibitor is preferably added in an amount ofabout 0.01 to about 5 mass % in the image-recording layer.

In the image-recording layer of the present invention, for example, ahigher fatty acid derivative such as behenic acid or behenic acid amidemay be added and localized on the surface of the image-recording layerduring drying after coating so as to prevent polymerization inhibitionby oxygen. The amount of the higher fatty acid derivative added ispreferably from about 0.1 to about 10 mass % based on the entire solidcontent of the image-recording layer.

The image-recording layer of the present invention may contain aplasticizer. Suitable examples of the plasticizer include phthalic acidesters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate,diisobutyl phthalate, diocyl phthalate, octyl capryl phthalate,dicyclohexyl phthalate, ditridecyl phthalate, butyl benzyl phthalate,diisodecyl phthalate and diallyl phthalate; glycol esters such asdimethyl glycol phthalate, ethyl phthalylethyl glycolate, methylphthalylethyl glycolate, butyl phthalylbutyl glycolate and triethyleneglycol dicaprylic acid ester; phosphoric acid esters such as tricresylphosphate and triphenyl phosphate; aliphatic dibasic acid esters such asdiisobutyl adipate, dioctyl adipate, dimethyl sebacate, dibutylsebacate, dioctyl azelate and dibutyl maleate; polyglycidylmethacrylate, triethyl citrate, glycerin triacetyl ester and butyllaurate. The plasticizer content is preferably about 30 mass % or lessin the image-recording layer.

For heightening interfacial adhesion by surface roughening treatment,and for the improvement of the hardened layer strength of an image areaand the on-press developability of a non-image area, the image-recordinglayer in the invention may contain inorganic fine particles.

As the inorganic fine particles, e.g., silica, alumina, magnesium oxide,titanium oxide, magnesium carbonate, calcium alginate and mixtures ofthese fine particles are preferably used.

The average particle size of the inorganic fine particles is preferablyfrom 5 nm to 10 μm, and more preferably from 0.5 to 3 μm. When theaverage particle size is in this range, the inorganic fine particles arestably dispersed in the image-recording layer, and the layer strength ofthe image-recording layer can be sufficiently maintained, so that anon-image area difficult to be soiled and excellent in hydrophilicitycan be formed.

These inorganic fine particles are easily available as commercialproducts of colloidal silica dispersion and the like.

The content of the inorganic fine particles is preferably 20 mass % orless to all the solids content of the image recording layer, and morepreferably 10 mass % or less.

For the improvement of on-press developability, the image-recordinglayer in the invention may contain hydrophilic low molecular weightcompounds. As the hydrophilic low molecular weight compounds,water-soluble organic compounds, such as glycols, e.g., ethylene glycol,diethylene glycol, triethylene glycol, propylene glycol, dipropyleneglycol, tripropylene glycol, and ether or ester derivatives of theseglycols, polyhydroxies, e.g., glycerol and pentaerythritol, organicamines, e.g., triethanolamine, diethanolamine and monoethanolamine, andsalts of these organic amines, organic sulfonic acids, e.g.,toluenesulfonic acid and benzene-sulfonic acid, and salts of theseorganic sulfonic acids, organic phosphonic acids, e.g., phenylphosphonicacid, and salts of phenylphosphonic acid, organic carboxylic acids,e.g., tartaric acid, oxalic acid, citric acid, malic acid, lactic acid,gluconic acid and amino acid, and salts of these organic carboxylicacids, and organic quaternary ammonium salts, e.g., tetraethylaminehydrochloride are exemplified.

Formation of image-recording layer:

As the method of incorporating the constitutional components ofimage-recording layer into an image-recording layer, some embodimentscan be used in the invention. One embodiment is a molecular dispersiontype image-recording layer of dissolving the constitutional componentsin an appropriate solvent and coating the resulting solution asdisclosed, e.g., in JP-A-2002-287334, and another embodiment is amicrocapsule type image-recording layer of encapsulating all or a partof the constitutional components in microcapsules and incorporating intothe image-recording layer as disclosed, e.g., in JP-A-2001-277740 andJP-A-2001-277742. In addition, in the microcapsule type image-recordinglayer, it is also possible to incorporate the constitutional componentsoutside the microcapsules. Here, it is a preferred embodiment of themicrocapsule type image-recording layer that hydrophobic constitutionalcomponents are encapsulated in microcapsules and hydrophilicconstituents are incorporated outside the microcapsules. As a furtherembodiment, an image recording layer containing crosslinking resinparticles, i.e., microgels, can be exemplified. The microgels cancontain image-recording layer constituents in the inside and/or on thesurface of the microgels. An embodiment where the microgels are reactivemicrogels having a polymerizable compound on the surface thereof isespecially preferred from the viewpoints of image-forming sensitivityand press life. For achieving better on-press developability, it ispreferred to contain microcapsules and/or microgels in animage-recording layer.

For the microencapsulation and/or microgelation of the constitutionalcomponents of the image-recording layer, well known methods can be used.For example, as the manufacturing method of microcapsules, a methodmaking use of coacervation as disclosed in U.S. Pat. Nos. 2,800,457 and2,800,458, an interfacial polymerization method as disclosed in U.S.Pat. No. 3,287,154, JP-B-38-19574 (the term “JP-B” as used herein refersto an “examined Japanese patent publication”), and JP-B-42-446, a methodby the precipitation of a polymer as disclosed in U.S. Pat. Nos.3,418,250 and 3,660,304, a method of using isocyanate polyol wallmaterials as disclosed in U.S. Pat. No. 3,796,669, a method of usingisocyanate wall materials as disclosed in U.S. Pat. No. 3,914,511, amethod of using urea-formaldehyde series or urea-formaldehyde-resorcinolseries wall materials as disclosed in U.S. Pat. Nos. 4,001,140,4,087,376 and 4,089,802, a method of using wall materials ofmelamine-formaldehyde resins, hydroxy cellulose and the like asdisclosed in U.S. Pat. No. 4,025,445, an in situ method by monomerpolymerization as disclosed in JP-B-36-9163 and JP-B-51-9079, a spraydrying method as disclosed in British Patent 930,422 and U.S. Pat. No.3,111,407, and an electrolytic dispersion cooling method as disclosed inBritish Patents 952,807 and 967,074 can be exemplified, but theinvention is not restricted to these methods.

The microcapsule and/or microgel walls preferably used in the inventionhave a three dimensional crosslinking structure and a property ofswelling with a solvent. From such a viewpoint, polyurea, polyurethane,polyester, polycarbonate, polyamide, and mixtures of these compounds arepreferably used as the microcapsule and/or microgel wall materials, andpolyurea and polyurethane are especially preferred. Further, a compoundhaving a crosslinkable functional group such as an ethylenic unsaturatedbond that can be introduced into the above binder polymers may beintroduced into microcapsule and/or microgel walls.

The average particle size of the microcapsules and/or microgel ispreferably from 0.01 to 3.0 μm, more preferably from 0.05 to 2.0 μm, andespecially preferably from 0.10 to 1.0 μm. Good resolution and agingstability can be obtained in this range of the average particle size.

The image-recording layer in the invention is formed by coating acoating solution prepared by dispersing or dissolving the abovenecessary constituents in a solvent according to any of the aboveembodiments. As the solvents used here, ethylene dichloride,cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol,ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethylacetate, 1-methoxy-2-propyl acetate, dimethoxyethane, methyl lactate,ethyl lactate, N,N-dimethylacetamide, N,N-dimethylformamide,tetramethylurea, N-methylpyrrolidone, dimethyl sulfoxide, sulforan,γ-butyrolactone, toluene, and water are exemplified, but the solventsare not limited thereto. These solvents are used alone or as a mixture.The concentration of the solids content of the coating solution ispreferably from 1 to 50 mass %.

It is also possible to form the image-recording layer in the inventionby preparing a plurality of coating solutions by dispersing ordissolving the same or different components described above in the sameor different solvents, and repeating the coating and drying a pluralityof times.

The coating weight of the image-recording layer (solids content) ispreferably from 0.3 to 1.5 g/m², and more preferably from 0.5 to 1.5g/m².

As the coating method, various coating methods can be used, e.g., barcoating, rotary coating, spray coating, curtain coating, dip coating,air knife coating, blade coating, and roll coating can be used.

Image-Recording Layer (2):

In the next place, the image-recording layer of the lithographicprinting plate precursors described in claims 7 to 16 is explained. Theimage-recording layer contains (A) an actinic ray absorber, (B) apolymerization initiator, and (D) a binder polymer, and is capable ofremoving with a printing ink or a fountain solution or both of them.

The same actinic ray absorber (A) and polymerization initiator (B) asdescribed in image-recording layer (1) can be used in image-recordinglayer (2).

(D) Binder Polymer:

The image-recording layer contains a polymer having an ethylene oxidegroup as the binder polymer.

Of such binder polymers, graft polymers having a main chain polymer anda side chain of polyethylene oxide (PEO), and block copolymers havingboth a PEO block and a non-PEO block are especially preferred.

It is preferred that the graft and block copolymers are amphipathic,that is, it is preferred to have both a hydrophilic segment and ahydrophobic segment, further, the graft and block copolymers themselvesare preferably water-insoluble. Although the reason is not clear, thecombination of a hydrophilic segment and a hydrophobic segment isimportant for widening the difference between an exposed area and anunexposed area.

The glass transition point Tg of the binder polymers for use in theinvention is preferably in the range of from −10 to 220° C. or so, morepreferably from 0 to 140° C. or so, and especially preferably from 10 to100° C. or so. Binder polymers having Tg of the above range are solids,and preferably non-elastomeric. The binder polymers may be crosslinkedbut preferably not crosslinked. The glass transition point Tg of themain chain polymer of the graft copolymer and the non-PEO block of theblock copolymer is preferably in the range of from 40 to 220° C. or so,more preferably from 50 to 140° C. or so, and especially preferably from60 to 130° C. or so.

The number average molecular weight of the graft and block copolymers ispreferably from 2,000 to 2,000,000 or so. The number average molecularweight (Mn) of the PEO segment is preferably in the range of from 500 to10,000 or so, more preferably in the range of from 600 to 8,000 or so,and especially preferably in the range of from 750 to 4,000 or so. Bymaking the Mn value about 500 or more, hydrophilic segments aresufficient, and aqueous development can be sufficiently accelerated.However, the ink receptivity in an image area decreases when the Mnvalue of the polyethylene oxide part is 10,000 or more.

The amount of PEO segments in the graft copolymer is generally from 0.5to 60 mass % or so, preferably from 2 to 50 mass % or so, morepreferably from 5 to 40 mass % or so, and especially preferably from 5to 20 mass % or so. The amount of PEO segments in the block copolymer isgenerally from 5 to 60 mass % or so, preferably from 10 to 50 mass % orso, and more preferably from 10 to 30 mass % or so. When the graft andblock copolymers are low in PEO segments, developability is liable tolower, on the other hand, an excess amount of PEO segments leads to thereduction of ink receptivity in an image area.

The binder polymer is present in an amount sufficient to maintain theimage-recording layer as a film. The amount of the binder polymer ispreferably 2 mass % or more to the image-recording layer, morepreferably in the range of from 5 to 90 mass %, and still morepreferably in the range of from 10 to 60 mass %. When the amount of thePEO segments in the binder polymer increases, aqueous developability isliable to be high. However, an excess amount of the PEO segments resultsin the reduction of ink receptivity in an image area.

It is preferred for the graft copolymer to have a hydrophobic highmolecular skeleton and a plurality of pendent groups represented by thefollowing formula.

-Q-W-Y

In the formula, Q represents a bifunctional linking group; W is selectedfrom the group consisting of a hydrophilic segment and a hydrophobicsegment; and Y is selected from the group consisting of a hydrophilicsegment and a hydrophobic segment, provided that when W is a hydrophilicsegment, Y is selected from the group consisting of a hydrophilicsegment and a hydrophobic segment, and when W is hydrophobic, Y is ahydrophilic segment.

The terminology of “graft” polymer or copolymer in the specification ofthe invention means a polymer having a group having a molecular weightof at least 200 as the side chain. Such a graft copolymer can beobtained by a grafting method using an anion, a cation, a nonion or afree radical, or by the polymerization or copolymerization of a monomerhaving such a group. The terminology of “polymer” in the specificationof the invention means high molecular weight or low molecular weightpolymers including an oligomer, a homopolymer and a copolymer. Theterminology of “copolymer” means a polymer derived from two or morekinds of different monomers. The terminology of “skeleton” means anatomic chain in a polymer having a plurality of pendent groups. As theexample of such a skeleton, a skeleton comprising carbon atoms aloneobtained from the polymerization function of an olefin-based unsaturatedmonomer is exemplified.

Each unit of the graft copolymer preferably comprises a repeating unitrepresented by the following formula.

In the formula, R¹ and R² are each selected from the group consisting ofH, alkyl, aryl, aralkyl, alkaryl, COOR⁵, R⁶CO, halogen and a cyanogroup. R⁵ and R⁶ each represents H or alkyl.

Q is selected from the group consisting of the following compounds.

In the above formulae, R³ is selected from the group consisting of H andalkyl.

R⁴ is selected from the group consisting of H, alkyl, halogen, cyano,nitro, alkoxyl, alkoxycarbonyl, acyl, and the combinations of thesegroups.

W is selected from the group consisting of a hydrophilic segment and ahydrophobic segment.

Y is selected from the group consisting of a hydrophilic segment and ahydrophobic segment.

Z is selected from the group consisting of H, alkyl, halogen, cyano,acyloxy, alkoxyl, alkoxycarbonyl, hydroxy-alkoxycarbonyl, acyl,aminocarbonyl, aryl and substituted aryl.

However, when W is a hydrophilic segment, Y is selected from the groupconsisting of a hydrophilic segment and a hydrophobic segment, and whenW is hydrophobic, Y is a hydrophilic segment.

In some embodiment of the invention, the graft copolymer of theinvention comprises primarily a hydrophobic main chain segment andprimarily a hydrophilic branched segment.

In another embodiment of the invention, the graft copolymer of theinvention comprises primarily a hydrophobic main chain segment, and abranched segment having both a hydrophilic segment and a hydrophobicsegment.

The hydrophilic segment W of the graft copolymer of the invention ispreferably a segment represented by the following formula.

In the above formulae, R⁷, R⁸, R⁹ and R¹⁰ each represents hydrogen.

R³ may be H or alkyl.

n is from 1 to 250, preferably from 2 to 120, and more preferably from 6to 60.

The hydrophobic segment in W may be any of —R¹²—, —O—R¹²—O—,—R³N—R¹²—NR³—, —OOC—R¹²—O— and —COO—R¹²—O—, wherein each R¹² representsstraight chain, branched chain or cyclic alkylene having from 6 to 120carbon atoms, haloalkylene having from 6 to 120 carbon atoms, arylenehaving from 6 to 120 carbon atoms, alkarylene having from 6 to 120carbon atoms, or aralkylene having from 6 to 120 carbon atoms, and R³may be H or alkyl.

The hydrophilic segment in Y may be any of H, R¹⁵, OH, OR¹⁶, COOH,COOR¹⁶, O₂CR¹⁶ and a segment represented by any of the followingformulae.

In the above formulae, R⁷, R⁸, R⁹ and R¹⁰ each represents hydrogen, R³may be any of H and alkyl, R¹³, R¹⁴, R¹⁵ and R¹⁶ each represents H, oralkyl having from 1 to 5 carbon atoms, and n is from 1 to 250,preferably from 2 to 120, and more preferably from 6 to 60.

The hydrophobic segment in Y may be any of straight chain, branchedchain or cyclic alkyl having from 6 to 120 carbon atoms, haloalkylhaving from 6 to 120 carbon atoms, aryl having from 6 to 120 carbonatoms, alkaryl having from 6 to 120 carbon atoms, aralkyl having from 6to 120 carbon atoms, OR¹⁷, COOR¹⁷ and O₂CR¹⁷, wherein R¹⁷ representsalkyl having from 6 to 20 carbon atoms.

As a preferred specific example, the graft copolymer has a repeatingunit represented by the following formula.

In the formula, R¹ and R² each represents H, alkyl, aryl, aralkyl,alkaryl, COOR⁵, R⁶CO, halogen or cyano, and R⁵ and R⁶ are each H oralkyl.

Q may be any one of the following compounds.

In the above formulae, R³ may be any of H and alkyl.

Each R⁴ may be any of H, alkyl, halogen, cyano, nitro, alkoxyl,alkoxycarbonyl, acyl, and the combinations of these groups.

W is selected from the group consisting of a hydrophilic segment and ahydrophobic segment.

Y is selected from the group consisting of a hydrophilic segment and ahydrophobic segment.

Z is selected from the group consisting of H, alkyl, halogen, cyano,acyloxy, alkoxyl, alkoxycarbonyl, hydroxy-alkoxycarbonyl, acyl,aminocarbonyl, aryl and substituted aryl. The substituent of thesubstituted aryl may be any of alkyl, halogen, cyano, alkoxyl andalkoxycarbonyl, and the alkyl group is preferably an alkyl group havingfrom 1 to 22 carbon atoms.

However, when W is a hydrophilic segment, Y is selected from the groupconsisting of a hydrophilic segment and a hydrophobic segment, and whenW is hydrophobic, Y is a hydrophilic segment.

Segment W may be a hydrophilic segment or a hydrophobic segment.

The hydrophilic segment may be any of the segments represented by thefollowing formulae.

In the formulae, R⁷, R⁸, R⁹ and R¹⁰ each represents hydrogen.

R³ may be any of H and alkyl.

n is from 1 to 250, preferably from 2 to 120, and more preferably from 6to 60.

The hydrophobic segment may be any of —R¹²—, —O—R¹²—O—, —R³N—R¹²—NR³—,—OOC—R¹²—O— and —COO—R¹²—O—, wherein each R¹² represents straight chain,branched chain or cyclic alkylene having from 6 to 120 carbon atoms,haloalkylene having from 6 to 120 carbon atoms, arylene having from 6 to120 carbon atoms, alkarylene having from 6 to 120 carbon atoms, oraralkylene having from 6 to 120 carbon atoms, and R³ may be H or alkyl.

Y may be a hydrophilic segment or a hydrophobic segment.

The hydrophilic segment may be any of H, R¹⁵, OH, OR¹⁶, COOH, COOR¹⁶,O₂CR¹⁶ and a segment represented by any of the following formulae.

In the above formulae, R⁷, R⁸, R⁹ and R¹⁰ each represents hydrogen, R³may be any of H and alkyl, R¹³, R¹⁴, R¹⁵ and R¹⁶ each represents H, oralkyl having from 1 to 5 carbon atoms, and n is from 1 to 250,preferably from 2 to 120, and more preferably from 6 to 60.

The hydrophobic segment in Y may be any of straight chain, branchedchain or cyclic alkyl having from 6 to 120 carbon atoms, haloalkylhaving from 6 to 120 carbon atoms, aryl having from 6 to 120 carbonatoms, alkaryl having from 6 to 120 carbon atoms, aralkyl having from 6to 120 carbon atoms, OR¹⁷, COOR¹⁷ and O₂CR¹⁷, wherein R¹⁷ representsalkyl having from 6 to 20 carbon atoms.

Another embodiment in which segment W-Y is represented by the followingformula is also preferred.

—(OCH₂CH₂)_(n)—OCH₃

Here, n is from 1 to 250, preferably from 2 to 120, and more preferablyfrom 6 to 60.

In the preferred embodiment above, the graft copolymer has, e.g., arepeating unit represented by the following formula.

Here, n is from 1 to 250, preferably from 2 to 120, and more preferablyfrom 6 to 60.

In another preferred embodiment, the graft copolymer has a repeatingunit represented by the following formula.

Here, n is from 1 to 250, preferably from 2 to 120, and more preferablyfrom 6 to 60.

Another preferred embodiment is that the main chain polymer of the graftcopolymer of the invention is comprised of a monomer unit selected fromthe group consisting of acrylic acid ester, methacrylic acid ester,styrene, acrylic acid, methacrylic acid, and combinations thereof. Themonomer unit is more preferably methyl methacrylate, allyl methacrylate,or a combination thereof.

The graft copolymer having a hydrophobic segment and/or a hydrophilicsegment can be synthesized according to the process comprising thefollowing procedures (A) and (B).

Procedure (A):

A polymerizable graft monomer is synthesized by reacting the followingcomponents (i) and (ii).

(i) A compound represented by the following formula:

H—W—Y

In the formula, W is selected from the group consisting of a hydrophilicsegment and a hydrophobic segment, Y is selected from the groupconsisting of a hydrophilic segment and a hydrophobic segment, providedthat when W is a hydrophilic segment, Y is selected from the groupconsisting of a hydrophilic segment and a hydrophobic segment, and whenW is a hydrophobic segment, Y is a hydrophilic segment.

(ii) A polymerizable monomer selected from the group consisting of thecompounds represented by the following formulae:

In the formulae, each R¹ is selected from the group consisting of H,alkyl, aryl, aralkyl, alkaryl, COOR⁵, R⁶CO, halogen and a cyano group.R⁵ and R⁶ each represents H or alkyl.

R⁴ is selected from the group consisting of H, alkyl, halogen, cyano,nitro, alkoxyl, alkoxycarbonyl, acyl, and the combinations of thesegroups.

X is a separable group forming a polymerizable graft monomer byseparation selected from glycidyloxy, and the group consisting ofhalogen, alkoxyl and aryloxy.

Procedure (B):

The synthesized polymerizable graft monomer and one or more comonomersare subjected to copolymerization with temperature and time sufficientto synthesize a graft copolymer. If necessary, the polymerizable graftmonomer and the comonomers may be brought into contact in the presenceof a catalyst.

As preferred comonomers, e.g., styrene, substituted styrene,α-methylstyrene, acrylic acid ester, methacrylic acid ester,acrylonitrile, acrylamide, methacrylamide, vinyl halide, vinyl ester,vinyl ether, and α-olefin can be exemplified.

Any monomers that can react with H—W-Y may be used as the preferredpolymerizable monomer, e.g., polymerizable monomers such asm-isopropenyl, α,α-dimethylbenzyl isocyanate, acryloyl chloride,methacryloyl chloride are exemplified. The reaction is typicallyperformed in the presence of a catalyst, e.g., a base, a tin compound,and a mixture thereof are preferably used. A Lewis acid or a protonicacid can be used if the reaction proceeds with an acid catalyst.

It is preferred that a compound represented by formula H—W—Y is one ormore compounds represented by the following formulae.

In the formulae, R⁷, R⁸, R⁹ and R¹⁰ each represents hydrogen.

R³ may be H or alkyl.

Y may be any of alkyl, acyloxy, alkoxyl and carboxyl groups.

n is from 1 to 250, preferably from 2 to 120, and more preferably from 6to 60.

The graft copolymer is typically obtained by free radicalcopolymerization of a graft monomer and a comonomer. The mass ratio ofthe comonomer and the graft monomer is preferably from 99/1 to 45/55 orso.

As another method, the graft copolymer can be synthesized by thesynthesis of a copolymer capable of grafting in the first place by thecopolymerization of the polymerizable monomer of the invention and oneor more comonomers with sufficiently necessary temperature and time, andthen grafting the resulting copolymer capable of grafting with a —W—Ygroup. Such grafting can be achieved by bringing the above copolymercapable of grafting into contact with the compound represented byformula H—W—Y in the presence of a catalyst.

Here, W may be a hydrophilic segment or a hydrophobic segment, Y may bea hydrophilic segment or a hydrophobic segment, provided that when W isa hydrophilic segment, Y may be a hydrophilic segment or a hydrophobicsegment, and when W is a hydrophobic segment, Y is a hydrophilicsegment.

The graft copolymer in the invention can be synthesized by the reactionof polyethylene glycol monoalkyl ether having a function of a hydroxylgroup or an amino group and a polymer having reactivity to a hydroxylgroup or an amino group such as acid chloride, isocyanate or an acidanhydride group. Further, the side chain may have a hydrophobic segmentbetween the PEO segment and the main chain, or the PEO side chain mayhave hydrophobic segments at terminals. The graft copolymer of theinvention may be synthesized according to the method disclosed in U.S.patent application Ser. No. 09/826,300.

The main chain polymer of the graft copolymer may be an addition typepolymer or a condensation type polymer. The addition type polymer ispreferably synthesized from acrylic acid and methacrylic acid ester,acrylic acid and methacrylic acid, acrylamides and methacrylamides,acrylonitrile and methacrylonitrile, styrene, vinyl phenol andcombinations thereof. The addition type polymer is more preferablysynthesized from styrene, methyl methacrylate, allyl acrylate, and allylmethacrylate, acrylic acid and methacrylic acid, and combinationsthereof. As the condensation type polymer, polyurethanes, epoxy resins,polyesters, polyamides, and phenolic polymers, e.g., phenol-formaldehyderesin and pyrogallol-acetone resin are preferred.

The binder polymer may comprise a mixture of graft copolymers each ofwhich comprises a main chain polymer and a polyethylene oxide sidechain. The main chain polymer of each graft copolymer is selected froman addition type polymer and a condensation type polymer. As preferredaddition type polymers, homopolymers and copolymers obtained from amonomer selected from the group consisting of acrylic acid ester andmethacrylic acid ester including allyl acrylate and allyl methacrylate,acrylic acid and methacrylic acid, acrylamides and methacrylamides,acrylonitrile and methacrylonitrile, styrene, vinyl phenol andcombinations thereof are exemplified. The examples of preferredcondensation type polymers include polyurethanes, epoxy resins,polyesters, polyamides, and phenolic polymers, e.g., phenol-formaldehyderesin and pyrogallol-acetone resin.

The block copolymers in the invention can be synthesized according toordinary methods such as anionic polymerization, cationicpolymerization, and free radical polymerization. Atomic transfer radicalpolymerization (ATRF) and reversible addition fragmentation chaintransfer polymerization (RAFT) are especially convenient methods. It isconvenient to synthesize PEO block copolymer according to the ATRPmethod as described in M. Ranger et al., Journal of Polymer Science,Part A, Polymer Chemistry, Vol. 39, pp. 3861-74, “to obtainsupermolecule assembly from a copolymer having definite two kinds ofblocks synthesized by general purpose atomic transfer radicalpolymerization method” (2001).

At least one of non-polyethylene oxide blocks of the block copolymer maybe an addition type polymer or a condensation type polymer. As additiontype polymers, homopolymers or copolymers obtained from a monomerselected from acrylic acid ester and methacrylic acid ester such asallyl acrylate and allyl methacrylate, acrylic acid and methacrylicacid, acrylamides and methacrylamides, acrylonitrile andmethacrylonitrile, styrene, and vinyl phenol are preferred. Ascondensation type polymers, polyurethanes, epoxy resins, polyesters,polyamides, and polyureas are preferred.

In one preferred embodiment of the invention, at least onenon-polyethylene oxide block of the block copolymer does not have apolyalkylene oxide segment. As another preferred embodiment, at leastone non-polyethylene oxide block comprises a homopolymer or a copolymerobtained from a monomer selected from the group consisting of methylmethacrylate, allyl acrylate and allyl methacrylate, acrylic acid andmethacrylic acid, styrene, vinyl phenol, and combinations thereof.

As described above, the binder polymer may comprise a mixture of blockcopolymers each having at least one PEO block and at least one non-PEOblock. Further, the binder polymer may comprise a mixture of a blockcopolymer and a graft copolymer as described above.

In another embodiment of the invention, the image-recording layer maycontain discontinuous particles. The particles may contain a mixture ofa plurality of copolymers including combinations of possible variousmonomer units. The discontinuous particles are preferably particles ofthe binder polymer suspended in the image-recording layer. An embodimentof the binder polymer has at least one graft copolymer is especiallypreferred. The particle size of the particles in a suspension solutionmay be from 60 to 300 nm or so. The existence of such discontinuousparticles shows the tendency of accelerating the developability of anunexposed area.

Other components:

Besides (A) an actinic ray absorber, (B) a polymerization initiator, and(D) a binder polymer, (C) a polymerizable compound can be incorporatedinto the image-recording layer in the invention. Further, if necessary,the image-recording layer may contain additives, e.g., a surfactant, acolorant, a printing-out agent, a polymerization inhibitor (a thermalpolymerization preventive), a higher fatty acid derivative, aplasticizer, inorganic fine particles, and a low molecular weighthydrophilic compound. As a polymerizable compound (C) and theseadditives, the same compounds as those described in the explanation ofthe image-recording layer (1) can be used.

The image-recording layer can be formed in the same manner as describedin the image-recording layer (1).

Image-recording layer (3):

In the next place, the image-recording layer of the lithographicprinting plate precursors described in claims 17 to 23 is explained. Theimage-recording layer contains, as essential components, (E) an infraredabsorber and (F) an iodonium salt. The components and the like of theimage-recording layer containing these components are described indetail below.

(E) Infrared Absorber:

The infrared absorbers used in the lithographic printing plateprecursors described in claims 17 to 23 are dyes or pigments havingabsorption maximum at wavelengths of 760 to 1,200 nm, and infraredabsorbers whose absorbance at any wavelength of from 400 to 700 nmchanges by 0.05 or more by the action of radicals can be used with nolimitation.

The visibility of a printing plate becomes good when the variation inabsorbance at any wavelength of from 400 to 700 nm is 0.05 or more,preferably 0.08 or more, more preferably 0.11 or more, and especiallypreferably 0.14 or more.

The visibility of a printing plate is improved when the variation inabsorbance occurs in the visible region of from 400 to 700 nm,preferably from 450 to 680 nm, more preferably from 500 to 660 nm.

As dyes used as infrared absorbers, commercially available dyes andwell-known dyes described in literatures, e.g., Senryo Binran (DyeHandbook), compiled by Yuki Gosei Kagaku Kyokai (1970) can be used.Specifically, azo dyes, metal complex azo dyes, pyrazolone azo dyes,naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carboniumdyes, quinoneimine dyes, methine dyes, cyanine dyes, squaryliumdyestuffs, pyrylium salts and metal thiolate complexes are exemplified.

As pigments for use in the invention, commercially available pigmentsand the pigments described in Color Index (C.I.) Binran (Color IndexBulletin), Shaishin Ganryo Binran (The Latest Pigment Handbook),compiled by Nippon Ganryo Gijutsu Kyokai (1977), Shaishin Ganryo OyoGijutsu (The Latest Pigment Applied Techniques), CMC Publishing Co. Ltd.(1986), and Insatsu Ink Gijutsu (Printing Ink Techniques), CMCPublishing Co. Ltd. (1984) can be used.

An infrared absorber having absorption maximum at wavelengths of from400 to 700 nm changes to the oxidant of the infrared absorber byreaction with the radicals generated at the exposed area, whereby causesvariation in tint, so that those susceptible to oxidation are preferablyused in the invention. From such a point of view, the oxidationpotential is preferably 0.45 V (vs. SCE) or less, more preferably 0.40 V(vs. SCE) or less, and still more preferably 0.35 V (vs. SCE) or less.

Although there is no specific greatest lower bound in the oxidationpotential of infrared absorbers preferably used, the oxidation potentialis preferably 0.10 V (vs. SCE) or more, and more preferably 0.15 V (vs.SCE) or more, in view of the stability in the combination with aniodonium salt (F).

As such infrared absorbers, those having an electron donatingsubstituent at the chromophores of the absorbers are preferred to makethe oxidation potential small. As preferred electron donatingsubstituents, substituents having Hammett's σ_(para) value of −0.10 orless are exemplified. Specifically, an alkyl group (σ_(para) value: from−0.12 to −0.20 or so), e.g., a methyl group, an ethyl group, and apropyl group, a hydroxyl group (σ_(para) value: −0.37), an alkoxyl group(σ_(para) value: from −0.24 to −0.45 or so), e.g., a methoxy group, anethoxy group, a propyloxy group, and a butoxy group, an aryloxy group(σ_(para) value: −0.32 or so), e.g., a phenoxy group and a toluoyloxygroup, and a (substituted) amino group (σ_(para) value: from −0.50 to−0.35), e.g., an amino group, a methylamino group, an ethylamino group,a butylamino group, a dimethylamino group, a diethylamino group, aphenylamino group, and a diphenylamino group are exemplified, and analkoxyl group and a (substituted) amino group having a large electrondonating property are especially preferred.

From the viewpoint of extending the conjugated system of a chromophoreto lessen oxidation potential, substituents having an aromatic grouplinked via a hetero atom are also exemplified as preferred substituents.As the hetero atoms for linking an aromatic group, a nitrogen atom, anoxygen atom, a phosphorus atom, a sulfur atom and a selenium atom areexemplified, and an especially preferred hetero atom is a sulfur atom.

As the aromatic groups to be linked, a hydrocarbon aromatic group, e.g.,a phenyl group, a naphthyl group and an anthranyl group, and aheterocyclic group, e.g., a furyl group, a thienyl group, a pyrazolylgroup, a triazolyl group, an indolyl group, and a benzothiazolyl groupare exemplified, and a heterocyclic group is especially preferred. Asubstituent may be substituted on these aromatic groups, and preferredsubstituents are those having Hammett's σ_(para) value of −0.10 or less.

As the chromophores of infrared absorbers, polymethine dyestuffs, e.g.,a cyanine dyestuff and a (thio)pyrylium dyestuff are preferred from thestandpoints of absorption wavelength aptitude, solubility, stability,and potential characteristics, above all, a cyanine dyestuff isespecially preferred, and from the viewpoints of absorption wavelengthaptitude and potential aptitude, heptamethine cyanine dyestuffs havingan indolenine skeleton, a benzindolenine skeleton, a benzothiazoleskeleton, a benzoxazole skeleton, or a benzoselenazole skeleton areespecially preferred. These polymethine dyestuffs are generally cationicdyestuffs whose chromophores have positive electric charge, and betainetype dyestuffs also having negative electric charge in the chromophoresare also preferably used from the standpoint of making the oxidationpotential small. As the examples of betaine type dyestuffs, thosesubstituted with a (thio)-barbituric acid group on the polymethinechain, and those having a squarylium skeleton or a croconium skeletonincorporated into the polymethine chain are exemplified.

Of the dyestuffs having the chromophores as described above, thedyestuffs represented by any of the following formulae (D1) to (D5) arepreferably used.

In formula (D1), R¹ and R² each represents a hydrogen atom or ahydrocarbon group having from 1 to 12 carbon atoms, and R¹ and R² may bebonded to each other to form a cyclic structure, and the cyclicstructure formed is preferably a 5- or 6-membered ring; Ar¹ and Ar²,which may be the same or different, each represents an aromatichydrocarbon group which may have a substituent, as preferred aromatichydrocarbon groups, a benzene ring and a naphthalene ring areexemplified, and as preferred substituents, a hydrocarbon group having12 or less carbon atoms, a halogen atom, and an alkoxyl group having 12or less carbon atoms are exemplified; Y¹ and Y², which may be the sameor different, each represents a sulfur atom or a dialkylmethylene grouphaving 12 or less carbon atoms; R³ and R⁴, which may be the same ordifferent, each represents a hydrocarbon group having 20 or less carbonatoms which may have a substituent, and as preferred substituents, analkoxyl group having 12 or less carbon atoms, a carboxyl group and asulfo group are exemplified; R⁵, R⁶, R⁷ and R⁸, which may be the same ordifferent, each represents a hydrogen atom or a hydrocarbon group having12 or less carbon atoms, and a hydrogen atom is preferred for easyavailability; R⁹ and R¹⁰, which may be the same or different, eachrepresents an aromatic hydrocarbon group having from 6 to 10 carbonatoms which may have a substituent, an alkyl group having from 1 to 8carbon atoms, or a hydrogen atom, and R⁹ and R¹⁰ may be bonded to eachother to form a cyclic structure, and as the cyclic structure, thefollowing structures are exemplified.

In the above formulae, X⁻ represents a counter anion, provided that whenany of R¹ to R⁸ is substituted with a sulfo group, X⁻ is not necessary.The preferred examples of X⁻ are a halogen ion, a perchlorate ion, atetrafluoroborate ion, a hexafluorophosphate ion, and a sulfonate ionfor the stability of an image-recording layer coating solution, and aperchlorate ion, a hexafluorophosphate ion, and an arylsulfonate ion areparticularly preferred.

In formula (D2), R¹ to R⁸, Ar¹, Ar², Y¹, Y² and X⁻ respectively have thesame meaning as those in formula (D1); and Ar³ represents a monocyclicor polycyclic heterocyclic group having at least one of a nitrogen atom,an oxygen atom and a sulfur atom. Preferred heterocyclic groups areselected from the group consisting of a thiazole series, a benzothiazoleseries, a naphthothiazole series, a thianaphtheno-7′,6′,4,5-thiazoleseries, an oxazole series, a benzoxazole series, a naphthoxazole series,a selenazole series, a benzoselenazole series, a naphthoselenazoleseries, a thiazoline series, a 2-quinoline series, a 4-quinoline series,a 1-isoquinoline series, a 3-isoquinoline series, a benzimidazoleseries, a 3,3-dialkylbenzindolenine series, a 2-pyridine series, a4-pyridine series, a 3,3-dialkylbenz[e] indole series, a tetrazoleseries, a triazole series, a pyrimidine series, and a thiadiazoleseries. As particularly preferred heterocyclic groups, the followingstructures are exemplified.

In formula (D3), R¹ to R⁸, Ar¹, Ar², Y¹ and Y² respectively have thesame meaning as those in formula (D1); R¹¹ and R¹², which may be thesame or different, each represents a hydrogen atom, an allyl group, acyclohexyl group, or an alkyl group having from 1 to 8 carbon atoms; andZ represents an oxygen atom or a sulfur atom.

In formula (D4), R¹³ represents a substituent having the structure shownbelow; R¹⁴ and R¹⁵ each represents an alkyl group having from 1 to 8carbon atoms; and Y³ represents an oxygen atom or a sulfur atom.

In formula (D5), R³, R⁴, Ar¹, Ar², Y¹ and Y² respectively have the samemeaning as those in formula (D1).

Of the dyestuffs having the chromophores as above, the dyestuffsrepresented by formulae (D1) to (D3) are more preferred, and thedyestuff represented by formula (D1) is particularly preferred.

The oxidation potential of an infrared absorber in the invention is avalue measured by potentiometry using a hydrogen electrode, a glasselectrode, and a quinhydrone electrode as the indicator electrodes, anda saturated calomel electrode and a silver-silver chloride electrode asthe reference electrodes in a polar solvent, e.g., acetonitrile ormethanol, and the obtained value is converted to the value in terms of anormal calomel electrode.

The specific examples of infrared absorbers ([IR-1] to [IR-12]) havingan oxidation potential of 0.45 V (vs. SCE) or less that can bepreferably used in the invention are shown below with the oxidationpotential, but the invention is not restricted to these infraredabsorbers.

Incidentally, the oxidation potential of the following infrared absorberwas the value measured by using a rotating disc electrode of Pt as theindicator electrode, and an Ag/AgCl (silver-silver chloride) counterelectrode as the reference electrode in a polar solvent (0.1 MEt₄NClO₄/MeCN), and the obtained value was converted to the value interms of a normal calomel electrode as the reference electrode.

Oxidation Infrared Potential Absorber Structure (V vs. SCE) IR-1 

0.20 IR-2 

0.22 IR-3 

0.24 IR-4 

0.27 IR-5 

0.27 IR-6 

0.30 IR-7 

0.30 IR-8 

0.35 IR-9 

0.35 IR-10

0.35 IR-11

0.40 IR-12

0.44

When an infrared absorber having a low oxidation potential as above isused, the hardening property of the image-recording layer isconspicuously improved as compared with the time of using an infraredabsorber having a high oxidation potential. Although the reason for thisfact is not clear, it is thought that by using an infrared absorber lowin oxidation potential with an ionic radical generator, thedecomposition of radicals are accelerated, so that the polymerizationreaction proceeds rapidly and an image area excellent in strength isformed presumably.

Infrared absorbers may be used alone, or two or more kinds may be usedin combination. In addition, general purpose infrared absorbers havingan oxidation potential exceeding 0.45 V (vs. SCE) can be used incombination within the range of not impairing the effect of theinvention. In this case, the content of the general purpose infraredabsorbers is preferably 40 mass % or less in all the solids content ofthe infrared absorbers.

As infrared absorbers that can be used in combination, the dyes andpigments disclosed in JP-A-7-285275 and JP-A-10-268512 can beexemplified.

When the lithographic printing plate precursors in the invention areused as on-development type lithographic printing plates, if theprinting plate before exposure is colored, there are cases where thecolor is contaminated in ink and/or a fountain solution to therebychange the tint of a printed matter and reduce quality. For avoidingsuch a problem, it is preferred that a printing plate before exposure iscolorless or light-colored (preferably colorless). Accordingly, the caseof coloration where the absorbance at any wavelength of from 400 to 700nm of an infrared absorber increases at least by 0.05 or more ispreferred to the case of discoloration where the absorbance decreases by0.05 or more.

The addition amount of infrared absorbers is preferably in the range offrom 0.01 to 50 mass % to all the solids content of the image-recordinglayer, more preferably from 0.1 to 20 mass %, and especially preferablyfrom 1 to 10 mass %.

When a recording material is manufactured using these infraredabsorbers, it is preferred that the optical density at maximumabsorption in the infrared region is preferably in the range of from0.05 to 3.0. Since optical density is determined by the addition amountof the infrared absorbers and the thickness of the image-recordinglayer, prescribed optical density can be obtained by controlling bothconditions. The optical density of an image-recording layer can bemeasured according to ordinary methods. For example, a method of formingan image-recording layer having an arbitrarily determined dry thicknessnecessary as a lithographic printing plate on a transparent or whitesupport, and measuring the optical density with a transmission typeoptical densitometer, and a method of forming an image-recording layeron a reflective support, e.g., an aluminum support, and measuring thereflection density are exemplified.

(F) Iodonium Salt:

An iodonium salt is a radical generator that generates radicals by lightor heat, or both energies, and also has functions of initiating andaccelerating the polymerization of a compound having a polymerizableunsaturated group and, at the same time, oxidizing an infrared absorberto change to an infrared absorber oxidant having absorption maximum atwavelengths of from 400 to 700 nm. An iodonium salt compound preferablyused in the invention is represented by the following formula (RI-IV):

Ar⁴¹—I^(+—Ar) ⁴²Z⁴¹⁻  (RI-IV)

In formula (RI-IV), Ar⁴¹ and Ar⁴² each represents an aryl group having20 or less carbon atoms which may have a substituent.

As the examples of the substituents in the case where the aryl group hasa substituent, a halogen atom, a nitro group, an alkyl group having 12or less carbon atoms, an alkoxyl group having 12 or less carbon atoms,and an aryloxy group having 12 or less carbon atoms are exemplified. Ofthe substituents, those having an electron donating substituent arepreferred for their good coloring property. As preferred electrondonating substituents, substituents having Hammett's σ_(para) value of−0.10 or less are exemplified.

Specifically, an alkyl group (σ_(para) value: from −0.12 to −0.20 orso), e.g., a methyl group, an ethyl group, and a propyl group, ahydroxyl group (σ_(para) value: −0.37), an alkoxyl group (σ_(para)value: from −0.24 to −0.45 or so), e.g., a methoxy group, an ethoxygroup, a propyloxy group, and a butoxy group, an aryloxy group (σ_(para)value: −0.32 or so), e.g., a phenoxy group and a toluoyloxy group, and a(substituted) amino group (σ_(para) value: from −0.50 to −0.35), e.g.,an amino group, a methylamino group, an ethylamino group, a butylaminogroup, a dimethylamino group, a diethylamino group, a phenylamino group,and a diphenylamino group are exemplified, and an alkoxyl group and a(substituted) amino group having a large electron donating property areespecially preferred.

Z⁴¹⁻ represents a counter ion selected from the group consisting of anorganic anion, e.g., R—COO⁻, R—SO₃ ⁻, R—SO₂ ⁻, R—PO₃H⁻, R—OPO₃H⁻,R—PO₂H⁻ and R—OPO₂H⁻ (where R represents a hydrocarbon group having from1 to 30 carbon atoms, which may have a substituent), and an inorganicanion, e.g., F⁻, Cl⁻, Br⁻, I⁻, ClO₄ ⁻, BF₄ ⁻, PF₆ ⁻, SbF₆ ⁻, AsF₆ ⁻,H₂PO₃ ⁻, H₂PO₄ ⁻, HSO₃ ⁻, HSO₄ ⁻ and NO₃ ⁻. Of these anions, R—SO₃ ⁻,R—PO₃H⁻, R—OPO₃H⁻, ClO₄ ⁻, BF₄ ⁻, PF₆ ⁻, and NO₃ ⁻ are preferred forgood on-developability, and R—SO₃ ⁻ having a hydrocarbon groupsubstituted with a fluorine atom is especially preferred.

As the specific examples of the iodonium salt compounds represented byformula (RI-IV) that can be preferably used in the invention, compounds(I-2) to (I-6), (I-11), (I-12), (I-15), (I-20) and (I-21) describedabove as the specific examples of the compound represented by formula(RI-II) are exemplified, but it should not be construed that theinvention is restricted to these compounds.

The maximum absorption wavelength of iodonium salt (F) for use in theinvention is preferably 400 nm or less, more preferably 330 nm or less,and still more preferably 270 nm or less. By bringing an absorptionwavelength into the ultraviolet region as above, an image-recordingmaterial can be handled under a white light.

The addition amount of these iodonium salt compounds is preferably from0.1 to 50 mass % based on all the solids content of the materials of theimage-recording layer, more preferably from 0.5 to 30 mass %, and stillmore preferably from 1 to 20 mass %. Iodonium salt compounds may be usedalone, or two or more compounds may be used in combination.

Infrared absorber (E) and iodonium salt (F) in the invention are addedto the image-recording layer, but these components may be further addedto other layers, e.g., a protective layer and an undercoat layer. Bothcomponents may be microencapsulated and added to the image-recordinglayer or other layers.

Elements for Forming Printing Image:

As the element for forming a print image, the image-recording layer inthe invention can use at least either (A) an image-forming elementutilizing radical or cationic polymerization, or (B) an image-formingelement utilizing thermal fusion and thermal reaction of ahydrophobitizing precursor. When element (A) is used, a polymerizationsystem image-recording layer is obtained, and when element (B) is used,an image-recording layer of a hydrophobitizing precursor is obtained.These elements are described below.

(I) Image-Forming Element Using Polymerization:

Since polymerization system element is high in image-formingsensitivity, exposure energy can be effectively shared for the formationof a printing out image, so that polymerization system element ispreferred for obtaining a printing out image having a good visibility.

The polymerization system element comprises a polymerizable compound anda polymerization initiator as primary components.

Polymerizable Compound:

As the polymerizable compounds to be used, polymerizable compounds (C)in the above description of the image-recording layer of thelithographic printing plate precursor for use in a packaged body areexemplified. In addition to the above, as the specific examples of thecompounds having a vinyl ether group of polymerizable compound (C), thecompounds disclosed in JP-A-2002-29162 are exemplified. As the specificexamples, tetramethylene glycol divinyl ether, trimethylolpropanetrivinyl ether, tetraethylene glycol divinyl ether, pentaerythritoldivinyl ether, pentaerythritol trivinyl ether, pentaerythritoltetravinyl ether, 1,4-bis[2-(vinyloxy)-ethyloxy]benzene,1,2-bis[2-(vinyloxy)ethyloxy]benzene,1,3-bis[2-(vinyloxy)ethyloxy]benzene,1,3,5-tris[2-(vinyloxy)ethyloxy]benzene,4,4′-bis[2-(vinyloxy)ethyloxy]-biphenyl,4,4′-bis[2-(vinyloxy)ethyloxy]diphenyl ether,4,4′-bis[2-(vinyloxy)ethyloxy]diphenylmethane,1,4-bis[2-(vinyloxy)ethyloxy]naphthalene,2,5-bis[2-(vinyloxy)-ethyloxy]furan,2,5-bis[2-(vinyloxy)ethyloxy]thiophene,2,5-bis[2-(vinyloxy)ethyloxy]imidazole,2,2-bis{4-[2-(vinyloxy)ethyloxy]phenyl}propane (bis[vinyloxyethyl]etherof bisphenol A), 2,2-bis[4-(vinyloxymethyloxy)phenyl]propane, and2,2-bis[4-(vinyloxy)phenyl]propane are exemplified.

These polymerizable compounds can be used in the same manner and theaddition amount as the above polymerizable compound (A).

Polymerization Initiator:

A polymerization initiator used generates a radical or an acid by theaction of heat of the infrared absorber absorbed infrared rays and/orlight, and initiates radical or cationic polymerization of thepolymerizable compound. The radical polymerization initiators (radicalgenerators) in the invention are selected from conventionally well-knownpolymerization initiators and compounds having a bond small in bondingand dissociation energy, and can be used in combination with the aboveiodonium salt compounds. For example, an onium salt, a triazine compoundhaving a trihalomethyl group, a peroxide, an azo-based polymerizationinitiator, an azide compound, a quinonediazide compound, a metallocenecompound, and an organic borate compound are exemplified, but thefollowing onium compounds are preferably used.

As the onium compounds preferably used in the invention as radicalgenerators in combination with iodonium salt compounds, a diazoniumsalt, a sulfonium salt, an ammonium salt, and a pyridinium salt areexemplified, and a diazonium salt and a sulfonium salt are especiallypreferably used. The combination with a sulfonium salt is especiallypreferred for the reason that the press life can be improved.

The diazonium salts and sulfonium salts preferably used in the inventionare the compounds represented by formulae (RI-I) and (RI-III) in theabove description of the image-recording layer of the lithographicprinting plate precursor for use in a packaged body.

The addition amount of the radical generator for use in combination withthe iodonium salt compound is preferably from 0.1 to 300 mass % to theaddition amount of the iodonium salt compound, more preferably from 1 to200 mass %, and still more preferably from 5 to 100 mass %.

Other Components:

If necessary, additives such as a binder polymer, a surfactant, acolorant, a polymerization inhibitor, a higher fatty acid derivative, aplasticizer, inorganic fine particles and a low molecular weighthydrophilic compound may further be added to the polymerization systemimage-recording layer of the invention. These additives are describedbelow.

Conventionally well-known binder polymers can be used in thepolymerization system image-recording layer in the invention with norestriction, and linear organic polymers having a film-forming propertyare preferably used. The examples of such binder polymers includeacrylic resins, polyvinyl acetal resins, polyurethane resins, polyurearesins, polyimide resins, polyamide resins, epoxy resins, methacrylicresins, polystyrene resins, novolak type phenolic resins, polyesterresin, synthetic rubber and natural rubber.

It is preferred that binder polymers have a crosslinking property forthe purpose of improving the layer strength of an image area. For givinga crosslinkable property to binder polymers, it is effective tointroduce a crosslinkable functional group such as an ethylenicunsaturated bond into the main chain or side chain of the polymers. Thecrosslinkable functional group may be introduced by copolymerization.

As the examples of the polymers having an ethylenic unsaturated bond inthe main chain of the molecule, poly-1,4-butadiene and poly-1,4-isopreneare exemplified.

As the examples of the polymers having an ethylenic unsaturated bond inthe side chain of the molecule, polymers of esters or amides of acrylicacid or methacrylic acid wherein the residue of the ester or amide (R of—COOR or —CONHR) has an ethylenic unsaturated bond are exemplified.

The examples of the residues having an ethylenic unsaturated bond (theabove R) include —(CH₂)—CR¹═CR²R³, —(CH₂O)—CH₂CR¹═CR²R³,—(CH₂CH₂O)—CH₂CR¹═CR²R³, —(CH₂)_(n)NH—CO—O—CH₂CR¹═CR²R³,—(CH₂)_(n)—O—CO—CR¹═CR²R³ and —(CH₂CH₂O)₂—X (wherein R¹, R² and R³ eachrepresents a hydrogen atom, a halogen atom, an alkyl group having from 1to 20 carbon atoms, an aryl group, an alkoxyl group or an aryloxy group,and R¹ and R² or R³ may be bonded to each other to form a ring, nrepresents an integer of from 1 to 10, and X represents adicyclopentadienyl residue).

The specific examples of the ester residues include —CH₂CH═CH₂(disclosed in JP-B-7-21633), —CH₂CH₂O—CH₂CH═CH₂, —CH₂C(CH₃)═CH₂,—CH₂CH═CH—C₆H₅, —CH₂CH₂OCOCH═CH—C₆H₅, —CH₂CH₂—NHCOO—CH₂CH═CH₂ and—CH₂CH₂O—X (wherein X represents a dicyclopentadienyl residue).

The examples of the amido residues include —CH₂CH═CH₂, —CH₂CH₂—Y(wherein Y represents a cyclohexene residue), and —CH₂CH₂—OCO—CH═CH₂.

When free radicals (polymerization initiating radicals or the grownradicals of a polymerizable compound in the polymerization process) areadded to the crosslinkable functional groups of a binder polymer havinga cros slinking property, addition polymerization occurs directlybetween the polymers or via the polymeric chains of the polymerizablecompound, as a result, crosslinking is formed between the molecules ofthe polymers, and the binder polymer is hardened. Alternatively, theatoms in the polymer (e.g., the hydrogen atoms on the carbon atomscontiguous to the crosslinkable functional groups) are extracted by freeradicals and polymer radicals are grown, and the polymer radicals arebonded to each other, whereby crosslinking is formed between the polymermolecules, so that the binder polymer is hardened.

The content of crosslinkable groups in a binder polymer (the content ofradical polymerizable unsaturated double bonds by iodometry) ispreferably from 0.1 to 10.0 mmol per 1 g of the binder polymer, morepreferably from 1.0 to 7.0 mmol, and most preferably from 2.0 to 5.5mmol. When the content of crosslinkable groups is in this range, goodsensitivity and good aging stability can be obtained.

From the viewpoint of the improvement of the on-press developability, itis preferred that binder polymers have high solubility or dispersibilityin ink and/or a fountain solution.

For improving the solubility or dispersibility in ink, binder polymersare preferably lipophilic, and for improving the solubility ordispersibility in a fountain solution, binder polymers are preferablyhydrophilic. Accordingly, it is also effective in the invention to use alipophilic binder polymer and a hydrophilic binder polymer incombination.

As hydrophilic binder polymers, binder polymers having a hydrophilicgroup, e.g., a hydroxyl group, a carboxyl group, a carboxylate group, ahydroxyethyl group, a polyoxyethyl group, a hydroxypropyl group, apolyoxypropyl group, an amino group, an aminoethyl group, an aminopropylgroup, an ammonium group, an amido group, a carboxymethyl group, asulfonic acid group and a phosphoric acid group are preferablyexemplified.

The specific examples of hydrophilic binder polymers include gum arabic,casein, gelatin, starch derivative, soya gum, carboxymethyl celluloseand the sodium salt thereof, cellulose acetate, sodium alginate, vinylacetate-maleic acid copolymers, styrene-maleic acid copolymers,polyacrylic acids and the salts thereof, polymethacrylic acids and thesalts thereof, homopolymers and copolymers of hydroxyethyl methacrylate,homopolymers and copolymers of hydroxyethyl acrylate, homopolymers andcopolymers of hydroxypropyl methacrylate, homopolymers and copolymers ofhydroxypropyl acrylate, homopolymers and copolymers of hydroxybutylmethacrylate, homopolymers and copolymers of hydroxybutyl acrylate,polyethylene glycols, hydroxypropylene polymers, polyvinyl alcohols,hydrolyzed polyvinyl acetate having a hydrolysis degree of 60 mol % ormore, preferably 80 mol % or more, polyvinyl formal, polyvinyl butyral,polyvinyl pyrrolidone, homopolymers and copolymers of acrylamide,homopolymers and copolymers of methacrylamide, homopolymers andcopolymers of N-methylolacrylamide, alcohol-soluble nylon, polyether of2,2-bis(4-hydroxyphenyl)propane and epichlorohydrin, homopolymers andcopolymers of 2-acrylamide-2-methyl-1-propanesulfonic acid, andhomopolymers and copolymers of 2-methacryloyloxyethyl-sulfonic acid.

The binder polymers preferably have a mass average molecular weight ofpreferably 5,000 or higher, more preferably from 10,000 to 300,000, anda number average molecular weight of preferably 1,000 or higher, morepreferably from 2,000 to 250,000. The polydisperse degree (mass averagemolecular weight/number average molecular weight) is preferably from 1.1to 10.

The binder polymers may be any of random polymers, block polymers andgraft polymers, but random polymers are preferred. The binder polymersmay be used alone or as a mixture of two or more.

The content of the binder polymers is preferably from 10 to 90 mass % tothe total solids content of the image-recording layer, more preferablyfrom 20 to 80 mass %, and still more preferably from 30 to 70 mass %.When the binder polymers are used in this range, preferred strength ofan image area and good image-forming property can be obtained.

It is preferred to use a polymerizable compound and the binder polymerin mass ratio of from 1/9 to 7/3.

Additives:

As the additives that can be used in the polymerization system imagerecording, e.g., a surfactant, a polymerization inhibitor, a higherfatty acid derivative, a plasticizer, inorganic fine particles, and alow molecular weight compound, the compounds described in the aboveexplanation of the image-recording layer of the lithographic printingplate precursor for use in a packaged body are exemplified. Preferably,the image-recording layer does not contain a compound that changes itscolor by an ancion of an acid, base or radical.

Formation of Polymerization System Image-Recording Layer:

As the method of incorporating the constitutional components ofimage-recording layer into an image-recording layer, some embodimentscan be used in the invention. One embodiment is a molecular dispersiontype image-recording layer of dissolving the constitutional componentsin an appropriate solvent and coating the resulting solution asdisclosed, e.g., in JP-A-2002-287334, and another embodiment is amicrocapsule type image-recording layer of encapsulating all or a partof the constitutional components in microcapsules and incorporating intothe image-recording layer as disclosed, e.g., in JP-A-2001-277740 andJP-A-2001-277742. In addition, in the microcapsule type image-recordinglayer, it is also possible to incorporate the constitutional componentsoutside the microcapsules. Here, it is a preferred embodiment of themicrocapsule type image-recording layer that hydrophobic constitutionalcomponents are encapsulated in microcapsules and hydrophilicconstituents are incorporated outside the microcapsules. Further,infrared absorber (E) and iodonium salt (F) can also bemicroencapsulated. As a further embodiment, an image recording layercontaining crosslinking resin particles, i.e., microgels, can beexemplified. The microgels can contain a part of image recording layerconstituents in the inside and/or on the surface of the microgels. Anembodiment where the microgels are reactive microgels having apolymerizable compound on the surface thereof is especially preferredfrom the viewpoints of image-forming sensitivity and press life.

For achieving better on-press developability, it is preferred that theimage-recording layer is a microcapsule type or a microgel typeimage-recording layer.

The methods for the microencapsulation or microgelation of theconstitutional components of the image-recording layer, the preferredaverage sizes of microcapsules and microgels, the methods of preparationand coating of the image-recording layer coating solution are the sameas described in the above explanation of the image-recording layer ofthe lithographic printing plate precursor for use in a packaged body.

The coating amount of the image-recording layer (solids content) on asupport obtained after coating and drying varies according to use, butgenerally preferably from 0.3 to 3.0 g/m². In this range of the coatingamount, good sensitivity and good film characteristics of theimage-recording layer can be obtained.

(II) Image-Forming Element of Hydrophobitizing Precursor:<Hydrophobitizing Precursor>

Hydrophobilizing precursors in the invention are fine particles capableof converting a hydrophilic image-recording layer to hydrophobic uponheating. Such fine particles are preferably at least one kind of fineparticles selected from thermoplastic polymer fine particles andthermo-reactive polymer fine particles. Further, the fine particles maybe microgels or microcapsules encapsulating a compound having athermo-reactive group.

As the thermoplastic polymer fine particles used in the invention, thethermoplastic polymer fine particles described in Research Disclosure,No. 33303, January (1992), JP-A-9-123387, JP-A-9-131850, JP-A-9-171249JP-A-9-171250, and EP 931647 can be preferably exemplified. The specificexamples of the polymers constituting these polymer fine particlesinclude homopolymers or copolymers of monomers such as ethylene,styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methylmethacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile,and vinyl carbazole, and mixtures thereof. Of these polymers,polystyrene and polymethyl methacrylate are more preferred.

The average particle size of the thermoplastic polymer fine particlesfor use in the invention is preferably from 0.01 to 2.0 μm. As thesynthesizing methods of these thermoplastic polymer fine particles, amethod of dissolving the above compounds in a water-insoluble organicsolvent, mixing and emulsifying the resulting solution with an aqueoussolution containing a dispersant, and applying heat to the emulsion tothereby solidify the emulsion to a fine particle state with volatizingthe organic solvent (a dissolution dispersion method) can be used, inaddition to an emulsion polymerization method and a suspensionpolymerization method.

As the thermo-reactive polymer fine particles used in the invention,thermosetting polymer fine particles and polymer fine particles having athermo-reactive group are exemplified.

As the thermosetting polymer fine particles, resins having a phenolicskeleton, urea resins (e.g., resins obtained by the resinification ofurea or urea derivatives, e.g., methoxymethylated urea, with aldehydes,e.g., formaldehyde), melamine resins (e.g., resins obtained by theresinification of melamine or melamine derivatives with aldehydes, e.g.,formaldehyde), alkyd resins, unsaturated polyester resins, polyurethaneresins, and epoxy resins can be exemplified. Of these resins, resinshaving a phenolic skeleton, melamine resins, urea resins and epoxyresins are especially preferred.

As preferred resins having a phenolic skeleton, e.g., phenolic resinsobtained by resinifying phenol or cresol with aldehydes, e.g.,formaldehyde, hydroxystyrene resins, and polymers and copolymers ofmethacrylamide or acrylamide or methacrylate or acrylate having aphenolic skeleton such as N-(p-hydroxyphenyl)methacrylamide andp-hydroxyphenyl methacrylate can be exemplified.

The average particle size of the thermosetting polymer fine particlesfor use in the invention is preferably from 0.01 to 2.0 μm. Thesethermosetting polymer fine particles can be easily obtained by adissolution dispersion method, but a thermosetting polymer may be madefine particles when the thermosetting polymer is synthesized. Theinvention is not limited to these methods.

As the thermo-reactive group of the polymer fine particles having athermo-reactive group used in the invention, functional groups showingany reaction can be used so long as chemical bonds are formed. Ethylenicunsaturated groups showing a radical polymerization reaction (e.g., anacryloyl group, a methacryloyl group, a vinyl group, an allyl group,etc.), cationic polymerizable groups (e.g., a vinyl group, a vinyloxygroup, etc.), isocyanate groups showing an addition reaction or blocksthereof, epoxy groups, vinyloxy groups and functional groups havingactive hydrogen atoms of the other side compounds of the reaction (e.g.,an amino group, a hydroxyl group, a carboxyl group, etc.), carboxylgroups showing a condensation reaction and hydroxyl groups and aminogroups of the other side compounds of the reaction, and acid anhydridesshowing a ring opening addition reaction and amino groups and hydroxylgroups of the other side compounds of the reaction can be preferablyexemplified.

These functional groups may be introduced into polymer fine particles inthe time of polymerization or they may be added after polymerization bya polymeric reaction.

When functional groups are introduced in the time of polymerization, itis preferred that the monomers having these functional groups areemulsion polymerized or suspension polymerized. The specific examples ofthe monomers having the functional groups include allyl methacrylate,allyl acrylate, vinyl methacrylate, vinyl acrylate, 2-(vinyloxy)ethylmethacrylate, p-vinyloxystyrene, p-[2-(vinyloxy)ethyl]-styrene, glycidylmethacrylate, glycidyl acrylate, 2-isocyanate ethyl methacrylate orblock isocyanate thereof by alcohol, 2-isocyanate ethyl acrylate orblock isocyanate thereof by alcohol, 2-aminoethyl methacrylate,2-aminoethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethylacrylate, acrylic acid, methacrylic acid, maleic anhydride, bifunctionalacrylate, and bifunctional methacrylate, but the invention is notlimited to these compounds.

In the invention, copolymers of these monomers and monomerscopolymerizable with these monomers not having thermo-reactive groupscan also be used. As the examples of copolymerizable monomers not havingthermo-reactive groups, styrene, alkyl acrylate, alkyl methacrylate,acrylonitrile and vinyl acetate can be exemplified, for instance, butmonomers not having thermo-reactive groups are not limited to thesemonomers.

As the polymeric reaction used in the case where the thermo-reactivegroups are introduced after polymerization, the polymeric reactionsdisclosed in WO 96/34316 can be exemplified.

Of the above polymer fine particles having thermo-reactive groups,polymers that are coalesced with each other by heat are preferred, andthose having hydrophilic surfaces and dispersible in water areparticularly preferred. It is preferred that the contact angle of a film(a water droplet in air) prepared by coating only polymer fine particlesand drying by a temperature lower than the solidification temperature islower than the contact angle of a film (a water droplet in air) preparedby drying by a temperature higher than the solidification temperature.For making the surfaces of polymer fine particles hydrophilic, it iseffective to let a hydrophilic polymer or oligomer, e.g., polyvinylalcohol or polyethylene glycol, or a hydrophilic low molecular weightcompound be adsorbed onto the surfaces of the polymer fine particles.However, the methods of surface hydrophilization treatment are notrestricted thereto.

The solidification temperature of these polymer fine particles havingthermo-reactive groups is preferably 70° C. or higher, but consideringthe aging stability, 100° C. or higher is more preferred. The averageparticle size of the polymer fine particles is preferably from 0.01 to2.0 μm, more preferably from 0.05 to 2.0 μm, and especially preferablyfrom 0.1 to 1.0 μm. Good resolution and aging stability can be obtainedin this range of average particle size.

As the thermo-reactive groups in the microcapsules or the microgelscontaining a compound having a thermo-reactive group for use in theinvention, the same thermo-reactive groups as used in the polymer fineparticles having thermo-reactive groups are preferably exemplified.

As the compound having thermo-reactive groups contained in themicrocapsules or microgels, the same compounds as the polymerizablecompounds described above are preferably used.

Besides the polymerizable compounds, compounds having an epoxy group canalso be exemplified as preferred compounds. As the compound having anepoxy group, compounds having two or more epoxy groups are preferred,and glycidyl ether compounds obtained by the reaction of polyhydricalcohol or polyhydric phenol with epichlorohydrin and prepolymersthereof, polymers and copolymers of glycidyl acrylate or glycidylmethacrylate can be exemplified.

The specific examples thereof include propylene glycol diglycidyl ether,tripropylene glycol diglycidyl ether, polypropylene glycol diglycidylether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidylether, diglycidyl ether of hydrogenated bisphenol A, hydroquinonediglycidyl ether, resorcinol diglycidyl ether, diglycidyl ether ofbisphenol A or epichlorohydrin polyaddition products, diglycidyl etherof bisphenol F or epichlorohydrin polyaddition products, diglycidylether of halogenated bisphenol A or epichlorohydrin polyadditionproducts, diglycidyl ether of biphenyl-type bisphenol or epichlorohydrinpolyaddition products, glycidyl etherified products of novolak resins,methyl methacrylate/glycidyl methacrylate copolymers, and ethylmethacrylate/glycidyl methacrylate copolymers.

Commercially available products of these compounds include, e.g.,Epicote 1001 (molecular weight: about 900, epoxy equivalence: 450-500,manufactured by Japan Epoxy Resin Co., Ltd.), Epicote 1002 (molecularweight: about 1,600, epoxy equivalence: 600-700), Epicote 1004(molecular weight: about 1,060, epoxy equivalence: 875-975), Epicote1007 (molecular weight: about 2,900, epoxy equivalence: 2,000), Epicote1009 (molecular weight: about 3,750, epoxy equivalence: 3,000), Epicote1010 (molecular weight: about 5,500, epoxy equivalence: 4,000), Epicote1100L (epoxy equivalence: 4,000), Epicote YX31575 (epoxy equivalence:1,200), Sumiepoxy ESCN-195×HN, ESCN-195XL and ESCN-195×F (manufacturedby Sumitomo Chemical Co., Ltd.), etc.

As the isocyanate compounds preferably used in the invention, tolylenediisocyanate, diphenylmethane diisocyanate, polymethylene polyphenylpolyisocyanate, xylylene diisocyanate, naphthalene diisocyanate,cyclohexane phenylene diisocyanate, isophorone diisocyanate,hexamethylene diisocyanate, cyclohexyl diisocyanate, and blockedproducts of these compounds with alcohol or amine can be exemplified.

As preferred amine compounds, ethylenediamine, diethylenetriamine,triethylenetetramine, hexamethylene-diamine, propylenediamine andpolyethyleneimine are exemplified.

As the compounds having a hydroxyl group preferably usable in theinvention, compounds having methylol groups at terminals, polyhydricalcohols such as pentaerythritol, and bisphenol.polyphenols areexemplified.

As the compounds having a carboxyl group preferably usable in theinvention, aromatic polycarboxylic acids, e.g., pyromellitic acid,trimellitic acid, and phthalic acid, and aliphatic polycarboxylic acids,e.g., adipic acid are exemplified. As the preferred acid anhydridespreferably used in the invention, pyromellitic anhydride andbenzophenone-tetracarboxylic anhydride are exemplified.

The compounds having a thermo-reactive group can be microencapsulatedand microgelated by the well-known methods described above in thepolymerization system image-recording layer.

Other Components:

For the purpose of improving on-press developability and the layerstrength of the image-recording layer itself, the image-recording layerin the invention can contain a Hydrophilic resin. As the hydrophilicresins, resins having a hydrophilic group, e.g., a hydroxyl group, anamino group, a carboxyl group, a phosphoric acid group, a sulfonic acidgroup, and an amido group are preferred. Further, since hydrophilicresins are crosslinked by the reaction with the thermo-reactive group ofa hydrophobitizing precursor to thereby increase image strength andresistance to press, it is preferred that the hydrophilic resins have agroup reactive with thermo-reactive groups. For example, whenhydrophobitizing precursors have a vinyloxy group or an epoxy group,hydrophilic resins having a hydroxyl group, a carboxyl group, aphosphoric acid group or a sulfonic acid group are preferred.Hydrophilic resins having a hydroxyl group or a carboxyl group areparticularly preferred.

As the specific examples of the hydrophilic resins, the polymersdescribed above as the hydrophilic binder polymers in the binderpolymers can be exemplified. The addition amount of the hydrophilicresins in the image-recording layer is preferably 20 mass % or less, andmore preferably 10 mass % or less.

The hydrophilic resins may be crosslinked in advance in such a degreethat an unexposed area can be subjected to on-press development. Theexamples of the crosslinking agents include aldehydes, e.g., glyoxal,melamine-formaldehyde resin, and urea-formaldehyde resin, methylolcompounds, e.g., N-methylolurea, N-methylolmelamine, and methylolatedpolyamide resin, active vinyl compounds, e.g., divinylsulfone andbis(β-hydroxyethylsulfonic acid), epoxy compounds, e.g.,epichlorohydrin, polyethylene glycol diglycidyl ether, polyamide,polyamine, epichlorohydrin addition product, andpolyamide-epichlorohydrin resin, ester compounds, e.g., monochloroaceticacid ester and thioglycolic acid ester, polycarboxylic acids, e.g.,polyacrylic acid and methyl vinyl ether/maleic acid copolymer, inorganiccrosslinking agents, e.g., boric acid, titanyl sulfate, Cu, Al, Sn, V,Cr salts, and modified polyamide-polyimide resins. In addition,crosslinking catalysts such as ammonium chloride, silane couplingagents, and titanate coupling agents can be used in combination.

The image-recording layer in the invention can contain reactionaccelerators for initiating or accelerating the reaction of thethermo-reactive groups. As such reaction accelerators, theabove-described polymerization initiators can be exemplified.

The reaction accelerators can be used in combination of two or more. Thereaction accelerators may be directly added to an image-recording layercoating solution, or may be added to the polymer fine particles. Thecontent of the reaction accelerators in the image-recording layer ispreferably from 0.01 to 20 mass % of the total solids content of theimage-recording layer, and more preferably from 0.1 to 10 mass %. Whenthe reaction accelerator is added in this range, on-press developabilityis not impaired and good reaction initiation or accelerating effect canbe ensured.

In the image-recording layer utilizing hydrophobitizing precursorseries, polyfunctional monomers can be added to the matrix of theimage-recording layer for further increasing the press life. As thepolyfunctional monomers, the polymerizable compounds exemplified abovecan be used. Trimethylolpropane triacrylate and pentaerythritoltriacrylate are preferred above all.

Further, the hydrophobitizing precursor series image-recording layer cancontain additives such as the surfactants, colorants, polymerizationinhibitors, higher fatty acid derivatives, plasticizers, inorganic fineparticles and low molecular weight hydrophilic compounds described inthe explanation of the image-recording layer of the lithographicprinting plate precursors for use in a packaged body, if necessary.

Formation of Hydrophobitizing Precursor Series Image Recording Layer:

Similarly to the case of the radical polymerization systemimage-recording layer, the hydrophobitizing precursor seriesimage-recording layer in the invention is formed by preparing a coatingsolution by dispersing or dissolving the above necessary components in asolvent, and coating the resulting coating solution on a support anddrying.

The coating weight (solids content) of the image recording layer on asupport obtained after coating and drying is generally preferably from0.5 to 5.0 g/m², although it differs according to uses.

A lithographic printing plate precursor capable of on-press developmentcan be manufactured by using the hydrophobitizing precursor seriesimage-recording layer.

On the other hand, by giving sufficient resistance to press to thehydrophobitizing precursor series image recording layer (a hydrophiliclayer having a crosslinking structure) even when the image-recordinglayer is unexposed, the lithographic printing plate precursor in theinvention can be applied to a non-processing (non-development) typelithographic printing plate precursor.

It is preferred for a hydrophilic layer having such a crosslinkingstructure to contain at least one kind of a hydrophilic resin having acros slinking structure and an inorganic hydrophilic binder resin formedby sol/gel conversion. Of these resins, the hydrophilic resin isdescribed first. By the addition of the hydrophilic resin, the affinityof the hydrophilic components in emulsion ink is increased and, at thesame time, the film strength of the image-recording layer itself is alsoimproved. As the hydrophilic resins, those having a hydrophilic group,e.g., hydroxyl, carboxyl, hydroxyethyl, hydroxypropyl, amino,aminoethyl, aminopropyl and carboxymethyl, are preferred.

As the specific examples of the hydrophilic resins, the polymersdescribed above as the hydrophilic binder polymers in the binderpolymers can be exemplified. By using these binder polymers bycrosslinking, a hydrophilic layer having a crosslinking structure can beobtained. As crosslinking agents used for forming a crosslinkingstructure, the compounds exemplified above as the crosslinking agentsare used.

As preferred embodiment of non-processing (non-development) typeimage-recording layer, an image-recording layer containing an inorganichydrophilic binder resin formed by sol/gel conversion can also beexemplified. Preferred sol/gel convertible binder resins are polymerswherein the bonding groups of polyvalent elements form a networkstructure, i.e., a three-dimensional crosslinking structure, via oxygenatoms and, at the same time, polyvalent metals also have hydroxyl groupsand alkoxyl groups not bonded and they are mixed and form resinousstructure. The systems are in a sol state at a stage abundant in alkoxylgroups and hydroxyl groups, and the network resinous structure comes toheighten with the advancement of dehydration condensation. Thepolyvalent bonding elements of the compounds having sol/gel convertiblehydroxyl groups and alkoxyl groups are aluminum, silicon, titanium andzirconium, and all of which can be used in the invention. More preferredsol/gel convertible systems are those using silicon, and particularlypreferred system is a sol/gel convertible system containing a silanecompound having at least one silanol group. A sol/gel convertible systemusing silicon is described below. Sol/gel conversions using aluminum,titanium and zirconium can also be carried out by the substitution ofthe silicon in the following description with respective elements.

Sol/gel convertible binder resins are preferably resins having asiloxane bond and a silanol group, and a coating solution of sol systemcontaining a compound having at least one silanol group is used in theimage-recording layer in the invention. Condensation and gelation of thesilanol group progress during coating and drying processes, and thestructure of a siloxane skeleton is formed.

An image-recording layer containing a sol/gel convertible binder resinand the above hydrophilic resins and crosslinking agents can be used incombination for the purpose of the improvement of physical properties,e.g., layer strength and the flexibility of the layer, and thebetterment of coating property.

A siloxane resin for forming a gel structure is represented by thefollowing formula (I), and a silane compound having at least one silanolgroup is represented by the following formula (II). A material added toan image recording layer need not be a silane compound represented byformula (II) alone and, in general, the material may comprise anoligomer of a silane compound partially condensed, or may be a mixtureof a silane compound represented by formula (II) and the oligomer.

A siloxane resin represented by formula (I) is formed by sol/gelconversion from the dispersion containing at least one silane compoundrepresented by formula (II). In formula (I), at least one of R⁰¹R⁰² andR⁰³ represents a hydroxyl group, and the remaining represent an organicresidue selected from R⁰ and Y in formula (II).

(R⁰)_(n)Si(Y)_(4-n)  (II)

In formula (II), R⁰ represents a hydroxyl group, a hydrocarbon group ora heterocyclic group; Y represents a hydrogen atom, a halogen atom,—OR¹—OCOR² or —N(R³)(R⁴); R¹ and R² each represents a hydrocarbon group;R³ and R⁴, which may be the same or different, each represents ahydrocarbon group or a hydrogen atom; and n represents 0, 1, 2 or 3.

R⁰ represents, as the hydrocarbon group or the heterocyclic group, e.g.,a straight chain or branched alkyl group having from 1 to 12 carbonatoms which may be substituted (e.g., a methyl group, an ethyl group, apropyl group, a butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group, a nonyl group, a decyl group, a dodecyl group,etc.; as the substituents of these groups, a halogen atom (a chlorineatom, a fluorine atom, a bromine atom), a hydroxyl group, a thiol group,a carboxyl group, a sulfo group, a cyano group, an epoxy group, an —OR¹group (R¹ represents a methyl group, an ethyl group, a propyl group, abutyl group, a heptyl group, a hexyl group, an octyl group, a decylgroup, a propenyl group, a butenyl group, a hexenyl group, an octenylgroup, a 2-hydroxyethyl group, a 3-chloropropyl group, a 2-cyanoethylgroup, an N,N-dimethylaminoethyl group, a 2-bromoethyl group, a2-(2-methoxyethyl)oxyethyl group, a 2-methoxycarbonylethyl group, a3-carboxyethyl group, a 3-carboxypropyl group, a benzyl group), an—OCOR″ group (R″ has the same meaning as R¹ above), a —COOR″ group, a—COR″ group, an —N(R′″)(R′″) group (R′″ represents a hydrogen atom orthe same meaning as R¹, and two R′″ may be the same or different), an—NHCONHR″ group, an —NHCOOR″ group, an —Si(R″)₃ group, and a —CONHR″group can be exemplified, and a plurality of substituents may besubstituted on the alkyl group), a straight chain or branched alkenylgroup having from 2 to 12 carbon atoms which may be substituted (e.g., avinyl group, a propenyl group, a butenyl group, a pentenyl group, ahexenyl group, an octenyl group, a decenyl group, a dodecenyl group,etc.; as the substituents of these groups, the same groups describedabove as the substituents of the alkyl group can be exemplified), anaralkyl group having from 7 to 14 carbon atoms which may be substituted(e.g., a benzyl group, a phenethyl group, a 3-phenylpropyl group, anaphthylmethyl group, a 2-naphthylethyl group; as the substituents ofthese groups, the same groups described above as the substituents of thealkyl group can be exemplified, and a plurality of substituents may besubstituted on the aralkyl group), an alicyclic group having from 5 to10 carbon atoms which may be substituted (e.g., a cyclopentyl group, acyclohexyl group, a 2-cyclohexylethyl group, a norbornyl group, anadamantyl group, etc.; as the substituents of these groups, the samegroups described above as the substituents of the alkyl group can beexemplified, and a plurality of substituents may be substituted), anaryl group having from 6 to 12 carbon atoms which may be substituted(e.g., a phenyl group, a naphthyl group, as the substituents of thesegroups, the same groups described above as the substituents of the alkylgroup can be exemplified, and a plurality of substituents may besubstituted), or a heterocyclic group containing at least one atomselected from a nitrogen atom, an oxygen atom and a sulfur atom whichmay be condensed (e.g., a pyran ring, a furan ring, a thiophene ring, amorpholine ring, a pyrrole ring, a thiazole ring, an oxazole ring, apyridine ring, a piperidine ring, a pyrrolidone ring, a benzothiazolering, a benzoxazole ring, a quinoline ring, a tetrahydrofuran ring,etc.; each of which may have a substituent, as the substituents of thesegroups, the same groups described above as the substituents of the alkylgroup can be exemplified, and a plurality of substituents may besubstituted).

The substituents of the —OR¹ group, —OCOR² group or —N(R³)(R⁴) grouprepresented by Y in formula (II) are as follows. In the —OR¹ group, R¹represents an aliphatic group having from 1 to 10 carbon atoms which maybe substituted (e.g., a methyl group, an ethyl group, a propyl group, abutyl group, a heptyl group, a hexyl group, a pentyl group, an octylgroup, a nonyl group, a decyl group, a propenyl group, a butenyl group,a heptenyl group, a hexenyl group, an octenyl group, a decenyl group, a2-hydroxyethyl group, a 2-hydroxypropyl group, a 2-methoxyethyl group, a2-(2-methoxyethyl)oxyethyl group, a 2-(N,N-dimethylamino)ethyl group, a2-methoxypropyl group, a 2-cyanoethyl group, a 3-methyloxypropyl group,a 2-chloroethyl group, a cyclohexyl group, a cyclopentyl group, acyclooctyl group, a chlorocyclohexyl group, a methoxycyclohexyl group, abenzyl group, a phenethyl group, a dimethoxybenzyl group, a methylbenzylgroup, a bromobenzyl group, etc.).

In the —OCOR² group, R² represents an aliphatic group of the samemeaning as R¹ has, or an aromatic group having from 6 to 12 carbon atomswhich may be substituted (as the aromatic group, those described abovein the aryl group represented by R can be exemplified). In the—N(R³)(R⁴) group, R³ and R⁴, which may be the same or different, eachrepresents a hydrogen atom or an aliphatic group having from 1 to 10carbon atoms which may be substituted (e.g., the same groups describedin R¹ of the —OR¹ group can be exemplified). More preferably, the totalnumber of the carbon atoms of R³ and R⁴ is not more than 16. As thespecific examples of the silane compound represented by formula (II),the following compounds can be exemplified, but the present invention isnot limited to these compounds.

Tetrachlorosilane, tetramethoxysilane, tetraethoxysilane,tetraisopropoxysilane, tetra-n-propylsilane, methyltrichlorosilane,methyltrimethoxysilane, methyltriethoxysilane, ethyltrichlorosilane,ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrichlorosilane,n-propyltrimethoxysilane, n-hexyltrimethoxysilane,n-decyltrimethoxysilane, phenyltrichlorosilane, phenyltrimethoxysilane,dimethoxyditriethoxysilane, dimethyldichlorosilane,dimethyldimethoxysilane, diphenyldimethoxysilane,phenylmethyldimethoxysilane, triethoxyhydrosilane,trimethoxyhydrosilane, vinyltrichlorosilane, vinyltrimethoxysilane,trifluoropropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane,γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane,γ-methacryloxypropyltrimethoxysilane,γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane,γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane,γ-mercaptopropyltriethoxysilane, andB-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

Together with a silane compound represented by formula (II), metalliccompounds capable of conjoining with resins to form a film at the timeof sol/gel conversion, e.g., Ti, Zn, Sn, Zr, Al, etc., can be used inthe image-recording layer in combination. The examples of the metalliccompounds for use for this purpose include, e.g., Ti(OR″)₄, TiCl₄,Zn(OR″)₂, Zn(CH₃COCHCOCH₃)₂, Sn(OR″)₄, Sn(CH₃COCHCOCH₃)₄, Sn(OCOR″)₄,SnCl₄, Zr(OR″)₄, Zr(CH₃COCHCOCH₃)₄, (NH₄)₂ZrO(CO₃)₂, Al(OR″)₃,Al(CH₃COCHCOCH₃), etc. (wherein R″ represents a methyl group, an ethylgroup, a propyl group, a butyl group, a pentyl group, a hexyl group).

For accelerating hydrolysis and polycondensation reaction of the silanecompound represented by formula (II) and the above metallic compound tobe used in combination, it is preferred to use an acidic catalyst or abasic catalyst together. As the catalyst, an acidic or basic compoundmay be used as it is, or may be dissolved in water or a solvent such asalcohol (hereinafter referred to as the acidic catalyst or the basiccatalyst). The concentration of the catalyst is not particularlyrestricted but when the concentration is high, hydrolysis andpolycondensation reaction are liable to become fast. However, when thebasic catalyst in high concentration is used, a precipitate is formed insome cases, so that the concentration of the basic catalyst ispreferably 1N (in terms of the concentration in an aqueous solution) orless.

The specific examples of the acidic catalysts include hydroghalogenicacid such as hydrochloric acid, carboxylic acids such as nitric acid,sulfuric acid, sulfurous acid, hydrogen sulfide, perchloric acid,hydrogen peroxide, carbonic acid, formic acid and acetic acid, andsulfonic acid such as benzenesulfonic acid. The specific examples of thebasic catalysts include ammoniacal bases such as aqueous ammonia, andamines such as ethylamine and aniline, but the catalysts are not limitedto these compounds.

As described above, an image-recording layer produced by the sol/gelmethod is particularly preferred as the constitution of theimage-recording layer according to the present invention. The details ofthe sol/gel method are described in Sumio Sakka, Sol/Gel Ho no Kagaku(Chemistry of Sol/Gel Method), Agune Shofu-Sha (1988) and HiroshiHirashima, Saishin Sol/Gel Ho ni yoru Kino-Sei Hakumaku Sakusei Gijutsu(Producing Techniques of Functional Thin Films by the Latest Sol/GelMethods), Sogo Gijutsu Center (1992).

The addition amount of the hydrophilic resins to the image recordinglayer having a crosslinking structure is preferably from 5 to 70 mass %of the solids content of the image-recording layer, more preferably from5 to 50 mass %.

Support:

Supports for use in the lithographic printing plate precursor in theinvention are not particularly limited and any supports can be used solong as they are dimensionally stable and plate-like materials. Forexample, paper, paper laminated with plastics (e.g., polyethylene,polypropylene, polystyrene, etc.), metal plates (e.g., aluminum, zinc,copper, etc.), plastic films (e.g., cellulose diacetate, cellulosetriacetate, cellulose propionate, cellulose butyrate, cellulose acetatebutyrate, cellulose nitrate, polyethylene terephthalate, polyethylene,polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), andpaper and plastic films laminated or deposited with the above metals canbe exemplified as the materials of the support. Preferred supports are apolyester film and an aluminum plate. Above all, aluminum sheets, whichare dimensionally stable and comparatively inexpensive, are preferred.

Aluminum plates are a pure aluminum plate, alloy plates containingaluminum as a main component and a trace amount of different elements,and aluminum or aluminum alloy thin films laminated with plastics. Theexamples of different elements contained in aluminum alloys includesilicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth,nickel, titanium, etc. The different element content in aluminum alloysis preferably 10 mass % or less. In the invention, a pure aluminum plateis preferred but 100% pure aluminum is difficult to produce from therefining technique, accordingly, an extremely small amount of differentelements may be contained. Thus, the compositions of aluminum platesused in the invention are not specified, and aluminum plates ofconventionally well known and commonly used materials can be optionallyused.

A support for use in the invention has a thickness of preferably from0.1 to 0.6 mm, more preferably from 0.15 to 0.4 mm, and still morepreferably from 0.2 to 0.3 mm

Prior to the use of an aluminum plate, it is preferred for the aluminumplate to be subjected to surface treatment, e.g., surface rougheningtreatment and anodizing treatment. By surface treatment, the improvementof hydrophilicity and the security of the adhesion of an image-recordinglayer and a support become easy. Prior to the surface rougheningtreatment of an aluminum plate, if necessary, degreasing treatment witha surfactant, an organic solvent or an alkaline aqueous solution iscarried out to remove the rolling oil on the surface of an aluminumplate.

Surface roughening treatment of the surface of an aluminum plate isperformed by various methods, e.g., mechanical surface rougheningtreatment, electrochemical surface roughening treatment (surfaceroughening treatment of electrochemically dissolving the surface), andchemical surface roughening treatment (surface roughening treatment ofchemically selectively dissolving the surface) are exemplified.

As the method of mechanical surface roughening treatment, well-knownmethods, e.g., a ball rubbing method, a brush abrading method, a blastabrading method, or a buffing method, can be used.

As the method of electrochemical surface roughening treatment, a methodof roughening in an electrolyte containing an acid such as ahydrochloric acid or a nitric acid by alternating current or directcurrent can be used. Further, a method of using mixed acids can be usedas disclosed in JP-A-54-63902.

The aluminum plate subjected to surface roughening treatment is, ifnecessary, subjected to alkali etching treatment with an aqueoussolution of potassium hydroxide or sodium hydroxide and neutralizingtreatment and then, if necessary, to anodizing treatment to increase theabrasion resistance of the surface.

Various electrolytes can be used in the anodizing treatment of analuminum plate for forming porous oxide film, and sulfuric acid,hydrochloric acid, oxalic acid, chromic acid and mixed acids of theseacids are generally used. The concentrations of these electrolytes arearbitrarily determined according to the kinds of electrolytes.

Anodizing treatment conditions vary according to electrolytes used andcannot be specified unconditionally, but in general preferably theconcentration of an electrolytic solution is from 1 to 80 mass %, theliquid temperature is from 5 to 70° C., the electric current density isfrom 5 to 60 A/dm², the voltage is from 1 to 100 V, electrolytic time isfrom 10 seconds to 5 minutes. The amount of the anodic oxide film formedis preferably from 1.0 to 5.0 g/m², more preferably from 1.5 to 4.0g/m². In this range of the amount of the anodic oxide film, good presslife and good scratch resistance of the non-image area of thelithographic printing plate can be obtained.

As the supports for use in the invention, supports subjected to surfacetreatments as above and having an anodic oxide film may be used as theyare, but for further improving the adhesion with the upper layer, ahydrophilic property, soiling resistance and a heat insulating property,enlarging treatment of the micro-pores of the anodic oxide film, sealingtreatment of the micro-pores, and hydrophilization treatment of thesurface by immersion in an aqueous solution containing a hydrophiliccompound as disclosed in JP-A-2001-253181 and JP-A-2001-322365 can bearbitrarily performed, if necessary.

As the hydrophilizing process, alkali metal silicate methods asdisclosed in U.S. Pat. Nos. 2,714,066, 3,181,461, 3,280,734 and3,902,734 are known. These methods comprise immersion processing of asupport in an aqueous solution of sodium silicate, or electrolyticprocessing. In addition, a method of processing an aluminum plate withpotassium fluorozirconate as disclosed in JP-B-36-22063, and methods ofprocessing with polyvinylphosphonic acid as disclosed in U.S. Pat. Nos.3,276,868, 4,153,461 and 4,689,272 are exemplified.

When a polyester film insufficient in a hydrophilic property of surfaceis used as a support in the invention, it is preferred to coat ahydrophilic layer to make the surface hydrophilic. As the hydrophiliclayers, a hydrophilic layer provided by coating a coating solutioncontaining the colloid of oxide or hydroxide of at least one elementselected from beryllium, magnesium, aluminum, silicon, titanium, boron,germanium, tin, zirconium, iron, vanadium, antimony and transitionmetals as disclosed in JP-A-2001-199175, a hydrophilic layer having anorganic hydrophilic matrix obtained by the crosslinking orpseudo-crosslinking of an organic hydrophilic polymer as disclosed inJP-A-2002-79772, a hydrophilic layer having an inorganic hydrophilicmatrix obtained by sol/gel conversion comprising hydrolysis andcondensation reaction of polyalkoxysilane, titanate, zirconate oraluminate, and a hydrophilic layer comprising an inorganic thin filmhaving a surface containing a metallic oxide are preferred. Of thesehydrophilic layers, a hydrophilic layer provided by coating a coatingsolution containing the colloid of oxide or hydroxide of silicon ispreferred.

When a polyester film is used as a support in the invention, it ispreferred to provide an antistatic layer on the hydrophilic layer sideof the support, or on the opposite side to the hydrophilic layer, or onboth sides. When an antistatic layer is provided between a support and ahydrophilic layer, the antistatic layer also contributes to the adhesionof the hydrophilic layer and the support. The polymer layers containingthe dispersion of metallic oxide fine particles and a matting agent asdisclosed in JP-A-2002-79772 can be used as the antistatic layers.

It is preferred that a support for use in the invention has a centralline average surface roughness of from 0.10 to 1.2 μm. In this range ofaverage surface roughness, good adhesion of the support and animage-recording layer, good press life and good soiling resistance canbe obtained.

The color density of a support is preferably from 0.15 to 0.65 in termsof a reflection density value. A good image forming property due toantihalation in the time of image exposure and a good plate-detectingproperty after development can be obtained when the color density of asupport is in this range.

Back Coat Layer:

After surface treatment of a support or after forming an undercoatlayer, if necessary, a backcoat can be provided on the back surface ofthe support.

As the backcoat, e.g., coating layers comprising organic polymercompounds as disclosed in JP-A-5-45885, and coating layers comprisingmetallic oxides obtained by hydrolysis and polycondensation of organicor inorganic metallic compounds as disclosed in JP-A-6-35174 arepreferably used. Alkoxy compounds of silicon, e.g., Si(OCH₃)₄,Si(OC₂H₅)₄, Si(OC₃H₇)₄, Si(OC₄H₉)₄, are preferably used for theinexpensiveness and easy availability of the materials.

Undercoat Layer:

In the lithographic printing plate precursor in the invention, ifnecessary, an undercoat layer can be provided between an image-recordinglayer and a support. In particular in the on-press development typelithographic printing plate precursor, the image-recording layer comesto be easily peeled off the support at an unexposed area by an undercoatlayer, so that on-press developability is improved. In the case ofinfrared laser exposure, since an undercoat layer functions as a heatinsulating layer, the heat generated by exposure does not diffuse to thesupport and is efficiently utilized, so that the improvement ofsensitivity can be contrived.

As the undercoat layer, specifically the silane coupling agent having anaddition polymerizable ethylenic double bond reactive group disclosed inJP-A-10-282679, and the phosphorus compounds having an ethylenic doublebond reactive group disclosed in JP-A-2-304441 are preferred.

As particularly preferred undercoat layer, polymer resins obtained bycopolymerizing a monomer having an adsorptive group/a monomer having ahydrophilic group/a monomer having a crosslinking group can beexemplified.

The essential component of polymer undercoating is an adsorptive grouponto a hydrophilic support surface. The presence or absence ofadsorptivity onto a hydrophilic support surface can be judged by thefollowing method.

A coating solution obtained by dissolving a test compound in an easilydissolving solvent is prepared, and the coating solution is coated on asupport in a dry weight of 30 mg/m² and dried. The support coated withthe test compound is thoroughly washed with the easily dissolvingsolvent, and the amount of the residue of the test compound not removedby washing is measured, from which the amount of the compound adsorbedonto the support is computed. The residual amount may be determined bydirectly measurement, or may be computed from the determination of thetest compound dissolved in the washing solution. The determination ofthe compound can be performed by fluorescent X-ray measurement,reflectance spectroscopic absorbance measurement, and liquidchromatography measurement. A compound having adsorptivity onto asupport is a compound that remains by 0.5 mg/m² or more after washing asabove.

Adsorptive groups onto a hydrophilic support surface are functionalgroups capable of causing chemical bonding (e.g., ionic bonding,hydrogen bonding, coordinate bonding, bonding by intermolecular force)with the substances present on a hydrophilic support surface (e.g.,metal, metallic oxide) or functional groups (e.g., a hydroxyl group).The adsorptive groups are preferably an acid radical or a cationicgroup.

The acid radical has an acid dissociation constant (pKa) of preferably 7or less. The examples of acid radicals include a phenolic hydroxylgroup, a carboxyl group, —PO₃H₂, —OPO₃H₂, —CONHSO₂—, —SO₂NHSO₂— and—COCH₂COCH₃, and phosphoric acid group (—OPO₃H₂ and —PO₃H₂) areespecially preferred. These acid radicals may be metal salts.

The cationic groups are preferably onium groups. The examples of oniumgroups include an ammonium group, a phosphonium group, an arsoniumgroup, a stibonium group, an oxonium group, a sulfonium group, aselenonium group, a stannonium group, and an iodonium group. An ammoniumgroup, a phosphonium group and a sulfonium group are preferred, and anammonium group and a phosphonium group are more preferred, and anammonium group is most preferred.

As especially preferred examples of monomers having an adsorptive group,the compounds represented by the following formula (III) or (IV) areexemplified.

In formula (III), R¹, R² and R³ each represents a hydrogen atom, ahalogen atom, or an alkyl group having from 1 to 6 carbon atoms. R¹, R²and R³ each preferably represents a hydrogen atom or an alkyl grouphaving from 1 to 6 carbon atoms, more preferably represents a hydrogenatom or an alkyl group having from 1 to 3 carbon atoms, and mostpreferably a hydrogen atom or a methyl group. R² and R³ each especiallypreferably represents a hydrogen atom.

In formula (III), X represents an oxygen atom (—O—) or an imino group(—NH—), and X more preferably represents an oxygen atom. In formula(III), L represents a divalent linking group. L preferably represents adivalent aliphatic group (an alkylene group, a substituted alkylenegroup, an alkenylene group, a substituted alkenylene group, analkynylene group, a substituted alkynylene group), a divalent aromaticgroup (an arylene group, a substituted arylene group), or a divalentheterocyclic group, or combinations of these groups with an oxygen atom(—O—), a sulfur atom (—S—), imino (—NH—), substituted imino (—NR—, whereR represents an aliphatic group, an aromatic group or a heterocyclicgroup), or carbonyl (—CO—).

The aliphatic group may have a cyclic structure or a branched structure.The carbon atoms of the aliphatic group is preferably from 1 to 20, morepreferably from 1 to 15, and most preferably from 1 to 10. As thealiphatic group, a saturated aliphatic group is preferred to anunsaturated aliphatic group. The aliphatic group may have a substituent,e.g., a halogen atom, a hydroxyl group, an aromatic group and aheterocyclic group.

The number of carbon atoms of the aromatic group is preferably from 6 to20, more preferably from 6 to 15, and most preferably from 6 to 10. Thearomatic group may have a substituent, e.g., a halogen atom, a hydroxylgroup, an aliphatic group, an aromatic group and a heterocyclic groupare exemplified as the examples of the substituents.

The heterocyclic group preferably has a 5- or 6-membered ring as aheterocyclic ring. Other heterocyclic ring, an aliphatic ring or anaromatic ring may be condensed with the heterocyclic ring. Theheterocyclic ring may have a substituent, e.g., a halogen atom, ahydroxyl group, an oxo group (═O), a thioxo group (═S), an imino group(═NH), a substituted imino group (═N—R, where R represents an aliphaticgroup, an aromatic group or a heterocyclic group), an aliphatic group,an aromatic group, and a heterocyclic group are exemplified as theexamples of the substituents.

L is preferably a divalent linking group containing a plurality ofpolyoxyalkylene structures. The polyoxyalkylene structures are morepreferably polyoxyethylene structures. In other words, it is preferredfor L to contain —(OCH₂CH₂)_(n)— (n is an integer of 2 or more).

In formula (III), Z represents a functional group adsorptive to ahydrophilic support surface. Y represents a carbon atom or a nitrogenatom. In the case where Y is a nitrogen atom and L is linked on Y toform a quaternary pyridinium group, the group itself shows adsorptivity,so that Z is not essential.

The adsorptive functional group is as described above.

In formula (IV), R¹, Y, L and Z have the same meaning as in formula(III).

The representative examples of the compounds represented by formula(III) or (IV) are shown below.

As preferred hydrophilic groups of the polymeric undercoating usable inthe invention, those having a sulfonic acid group showing a highhydrophilic property are exemplified. Specifically, sodium salts andamine salts of methallyloxy-benzenesulfonic acid,allyloxybenzenesulfonic acid, allylsulfonic acid, vinylsulfonic acid,p-styrenesulfonic acid, methallylsulfonic acid,acrylamido-t-butylsulfonic acid, 2-acrylamido-2-methylpropanesulfonicacid, and (3-acryloyloxypropyl)butylsulfonic acid are exemplified.Sodium 2-acrylamido-2-methylpropanesulfonate is preferred for thehydrophilic performance and easy handling on synthesis.

It is preferred that the polymer resins for the undercoat layer in theinvention have a crosslinking property for the improvement of adhesionwith the image area. For making the polymer resins for the undercoatlayer crosslinkable, a method of introducing a crosslinking functionalgroup, e.g., ethylenic unsaturated bond, to the side chain of thepolymer, and a method of forming a salt structure by a substituenthaving counter charge of the polar substituent of the polymer resin anda compound having an ethylenic unsaturated bond can be used.

As the examples of polymers having an ethylenic unsaturated bond in theside chain of a molecule, polymers of ester or amide of an acrylic acidor a methacrylic acid are exemplified, i.e., polymers in which theresidue of the ester or amide (R of —COOR or CONHR) has an ethylenicunsaturated bond.

The examples of residues having an ethylenic unsaturated bond (the aboveR) include —(CH₂)_(n)CR¹═CR²R³, —(CH₂O)_(n)CH₂CR¹═CR²R³,—(CH₂CH₂O)_(n)CH₂CR¹═CR²R³, —(CH₂)_(n)NH—CO—O—CH₂CR¹═CR²R³,—(CH₂)_(n)—O—CO—CR¹═CR²R³, and (CH₂CH₂O)₂—X (in the formulae, R¹, R² andR³ each represents a hydrogen atom, a halogen atom, an alkyl grouphaving from 1 to 20 carbon atoms, an aryl group, an alkoxyl group or anaryloxy group, and R¹ and R² or R³ may be bonded to each other to form aring, n represents an integer of from 1 to 10, and X represents adicyclopentadienyl residue).

The specific examples of ester residues include —CH₂CH═CH₂ (disclosed inJP-B-7-21633), —CH₂CH₂O—CH₂CH═CH₂, —CH₂C(CH₃)═CH₂, —CH₂CH═CH—C₆H₅,—CH₂CH₂OCOCH═CH—C₆H₅, —CH₂CH₂—NHCOO—CH₂CH═CH₂, and —CH₂CH₂O—X (wherein Xrepresents a dicyclopentadienyl residue).

The specific examples of amide residues include —CH₂CH═CH₂, —CH₂CF₁₂—Y(wherein Y represents a cyclohexene residue), and —CH₂CH₂OCO—CH═CH₂.

The content of crosslinkable groups in the polymer resin for theundercoat layer (the content of radical polymerizable unsaturated doublebonds by iodometry) is preferably from 0.01 to 10.0 mmol per gram of thepolymer resin, more preferably from 0.1 to 7.0 mmol, and most preferablyfrom 0.2 to 5.5 mmol. When the content of crosslinkable groups is inthis range, the compatibility of good sensitivity with soilingresistance, and good preservation stability can be ensured.

The polymer resin for the undercoat layer preferably has a mass averagemolecular weight of preferably 5,000 or higher, more preferably from10,000 to 300,000, and a number average molecular weight of preferably1,000 or higher, more preferably from 2,000 to 250,000. The polydispersedegree (mass average molecular weight/number average molecular weight)is preferably from 1.1 to 10.

The polymer resins for the undercoat layer may be any of a randompolymer, a block polymer and a graft polymer, but a random polymer ispreferred.

As the copolymer substituents of the polymers for the undercoatingusable in the invention, conventionally well known copolymersubstituents can be used with no limitation. As the hydrophiliccopolymer substituents, polymers having a hydrophilic group, e.g., ahydroxyl group, a carboxyl group, a carboxylate group, a hydroxyethylgroup, a polyoxyethyl group, a hydroxypropyl group, a polyoxypropylgroup, an amino group, an aminoethyl group, an aminopropyl group, anammonium group, an amido group, a carboxymethyl group, a sulfonic acidgroup and a phosphoric acid group are preferably exemplified.

The specific examples include sodium alginate, vinyl acetate-maleic acidcopolymers, styrene-maleic acid copolymers, polyacrylic acids and thesalts thereof, polymethacrylic acids and the salts thereof, homopolymersand copolymers of hydroxyethyl methacrylate, homopolymers and copolymersof hydroxyethyl acrylate, homopolymers and copolymers of hydroxypropylmethacrylate, homopolymers and copolymers of hydroxypropyl acrylate,homopolymers and copolymers of hydroxybutyl methacrylate, homopolymersand copolymers of hydroxybutyl acrylate, polyethylene glycols,hydroxypropylene polymers, polyvinyl alcohols, hydrolyzed polyvinylacetate having a hydrolysis degree of 60 mol % or more, preferably 80mol % or more, polyvinyl formal, polyvinyl butyral, polyvinylpyrrolidone, homopolymers and copolymers of acrylamide, homopolymers andcopolymers of methacrylamide, homopolymers and copolymers ofN-methylolacrylamide, polyvinyl pyrrolidone, alcohol-soluble nylon, andpolyether of 2,2-bis(4-hydroxyphenyl)propane and epichlorohydrin.

The polymer resin for the undercoat layer may be used alone, or two ormore polymer resin may be used as mixture. Two or more compounds havinga functional group adsorptive onto a hydrophilic support surface may beused in combination.

The coating amount of the undercoat layer (solids content) is preferablyfrom 0.1 to 100 mg/m², more preferably from 1 to 30 mg/m².

3. Lithographic printing method

In the lithographic printing method of the invention, the abovelithographic printing plate precursor of the invention is imagewiseexposed by exposure through a transparent original having a line imageand a dot image, or by laser scanning exposure by digital data. Asexposure light sources, e.g., a carbon arc lamp, a high-pressure mercurylamp, a xenon lamp, a metal halide lamp, a fluorescent lamp, a tungstenlamp, a halogen lamp, an ultraviolet laser, a visible laser and aninfrared laser are exemplified. Lasers are especially preferred, e.g., asolid state laser and a semiconductor laser radiating infrared rays offrom 760 to 1,200 nm, and a semiconductor laser radiating rays of from250 to 420 nm are exemplified.

In the lithographic printing plate precursors as claimed in claims 17 to23, a solid state laser and a semiconductor laser radiating infraredrays of from 760 to 1,200 nm are used.

When a laser is used, it is preferred to perform imagewise scanningexposure according to digital data. For expediting exposure time, it ispreferred to use a multi-beam laser device.

When an infrared laser is used, the exposure time per a pixel ispreferably not longer than 20 μsec. The quantity of irradiation energyis preferably from 10 to 300 mJ/cm².

When an ultraviolet laser is used, the staying time on pixels ispreferably as short as possible for suppressing the competitive reactionwith oxygen, preferably 1 msec or less, more preferably 500 μsec orless, and most preferably 100 μsec or less. The quantity of irradiationenergy is preferably from 0.1 to 10 mJ/cm².

In the lithographic printing method in the invention, as describedabove, after the lithographic printing plate precursor of the inventionis imagewise exposed with laser beams, printing can be carried out bysupplying oil ink and an aqueous component without being subjected todevelopment process.

Specifically, a method of subjecting a lithographic printing plateprecursor to laser exposure, and then mounting the exposed printingplate precursor on a printing press without undergoing developmentprocess and perform printing, and a method of mounting a lithographicprinting plate precursor on a printing press, and then exposing theprinting plate precursor with laser beams on the printing press, andperform printing without subjecting to development process areexemplified.

When a lithographic printing plate precursor is imagewise exposed withlaser beams and printing is performed by supplying oil ink and aqueouscomponent without being subjected to development process such as wetdevelopment process, the image-recording layer hardened by exposureforms an oil ink-accepting area having a lipophilic surface at theexposed area of the image-recording layer in the case of an on-pressdevelopment type lithographic printing plate precursor. On the otherhand, unhardened image-recording layer is dissolved or dispersed withthe supplied oil ink and/or aqueous component and removed at theunexposed area, whereby a hydrophilic surface is bared at that area. Asa result, the aqueous component adheres to the bared hydrophilicsurface, the oily ink adheres to the image-recording layer in theexposed area, and printing is initiated.

In the case of a non-processing type lithographic printing plateprecursor, since the unexposed area has a hydrophilic surface and theexposed area has been converted to a lipophilic surface, when an aqueouscomponent and/or oil ink are fed, the aqueous component is adhered tothe unexposed area and oil ink is adhered to the exposed areaselectively, so that it is possible to immediately perform printing.

Here, the one supplied first to the printing plate may be an aqueouscomponent or may be oil ink. However, for preventing the aqueouscomponent from becoming dirty by the image-recording layer at theunexposed area, it is preferred to supply oil ink first in the on-presstype lithographic printing plate precursor of the invention. As theaqueous component and the oil ink, a fountain solution and printing inkused in ordinary lithographic printing are respectively used.

Thus, the lithographic printing plate precursor is subjected to on-pressdevelopment on an offset press and used as it is in printing of a plentyof sheets.

EXAMPLE

The invention will be described with reference to Examples, but theinvention is not limited thereto.

Manufacture of Support:

For removing the rolling oil of the surface, an aluminum plate having athickness of 0.3 mm (material 1050) was subjected to degreasingtreatment with a 10 mass % sodium alminate aqueous solution at 50° C.for 30 seconds, and then the aluminum surface was subjected tobrush-graining with three nylon brushes planted with hairs having a hairdiameter of 0.3 mm and a suspension of pumice stone and water of amedian diameter of 25 μm (the specific gravity: 1.1 g/cm³), and thesurface of the plate was thoroughly washed with water. The plate wasimmersed in a 25 mass % sodium hydroxide aqueous solution at 45° C. for9 seconds for etching, and washed with water. After water washing, theplate was further immersed in a 20 mass % nitric acid aqueous solutionat 60° C. for 20 seconds, followed by washing with water. The etchedamount of the surface by graining was about 3 g/m².

Electrochemical surface roughening treatment was performed continuouslyby alternating voltage of 60 Hz. The electrolyte at this time was anaqueous solution containing 1 mass % of a nitric acid (containing a 0.5mass % of an aluminum ion) and the liquid temperature was 50° C. As thealternating current electric source waveform, trapezoidal rectangularwaveform alternating current was used, the time TP required for theelectric current value to reach the peak from 0 was 0.8 msec, the dutyratio was 1/1, and electrochemical surface roughening treatment wasperformed with a carbon electrode as the counter electrode. Ferrite wasused as the auxiliary anode. The electric current density was 30 A/dm²at a peak value of electric current, and 5% of the electric current fromthe electric source was diverted to the auxiliary anode. The quantity ofelectricity in nitric acid electrolysis was 175 C/dm² in the quantity ofelectricity with aluminum plate as the anode. The aluminum plate wasthen washed with water by spraying.

Subsequently, electrochemical surface roughening treatment of thealuminum plate was performed with an electrolyte of a 0.5 mass %hydrochloric acid aqueous solution (containing 0.5 mass % of an aluminumion) at a liquid temperature of 50° C. on the condition of the quantityof electricity of 50 C/dm² with the aluminum plate as the anode in thesame manner as in the nitric acid electrolysis. The plate was thenwashed with water by spraying. The plate was provided with 2.5 g/m² ofan anodic oxide film with a 15 mass % sulfuric acid (containing 0.5 mass% of an aluminum ion) as the electrolyte by the electric current densityof 15 A/dm², washed and dried to prepare support A. The central lineaverage surface roughness (Ra) of the plate measured with a needlehaving a diameter of 2 μm was 0.51 μm.

Undercoat layer coating solution (1) was coated on the above support Ato prepare a support having an undercoat layer to be used in thefollowing experiment. A support having a dry coating weight of 10 mg/m²was prepared as support B, and a support having a dry coating weight of6 mg/m² as support C.

Undercoat Layer Coating Solution (1):

  Undercoat compound (1) 0.017 g Methanol 9.00 g Water 1.00 g

Example 1 (1) Manufacture of Lithographic Printing Plate Precursor

The image-recording layer coating solution (1) having the compositionshown below was coated on support B with bar coating, dried at 100° C.for 60 seconds in an oven to form an image-recording layer having a drycoating weight of 1.0 g/m², whereby lithographic printing plateprecursor (1) was obtained. The central line average roughness (Ra) ofthe surface of the lithographic printing plate precursor having theimage recording layer measured with a needle having a diameter of 2 μmwas 0.40 μm, and the surface roughness of the side opposite to the sideon which the image-recording layer was coated was 0.25 μm.

Image-Recording Layer Coating Solution (1):

  Binder polymer (1) 0.162 g Polymerization initiator (1) 0.100 gInfrared absorber (1) 0.030 g Polymerizable compound, Aronix M-215 0.385g (manufactured by Toa Gosei Co., Ltd.) Fluorine surfactant (1) 0.044 gInorganic layered compound dispersion (1) 3.125 g prepared as followsMethyl ethyl ketone 1.091 g 1-Methyl-2-propanol 8.609 g Water 2.425 gMicrocapsules (1) synthesized as follows 2.640 g

Synthesis of Microcapsule (1):

As the Oil Phase Component, 10 G of the Addition Product ofTrimethylolpropane and xylene diisocyanate (Takenate D-110N, a 75 mass %ethyl acetate solution, manufactured by Mitsui Takeda Chemicals Inc.),6.00 g of Aronix M-215 (manufactured by To a Gosei Co., Ltd.), and 0.12g of Pionin A-41C (manufactured by Takemoto Oil & Fat) were dissolved in16.67 g of ethyl acetaate. As the aqueous phase component, 37.5 g of a 4mass % aqueous solution of PVA-205 was prepared. The oil phase componentand the aqueous phase component were mixed, and emulsified with ahomogenizer at 12,000 rpm for 10 minutes. The obtained emulsifiedproduct was added to 25 g of distilled water, stirred at roomtemperature for 30 minutes, and then stirred at 40° C. for 2 hours. Theconcentration of the solids content of the obtained microcapsulesolution was diluted with distilled water to reach 15 mass %. Theaverage particle size of the obtained microcapsule solution was 0.2 μm.

Preparation of Inorganic Layered Compound Dispersion (1):

To 193.6 g of ion exchange water was added 6.4 g of synthetic micaSomasif ME-100 (manufactured by CO—OP CHEMICAL CO., LTD.), and themixture was dispersed with a homogenizer until the average particle size(a laser scattering method) reached 3 μm.

(2) Manufacture of Packaged Body

Fifty sheets of the obtained lithographic printing plate precursors werelaminated in a manner that the surface of the side having animage-recording layer of one lithographic printing plate precursor andthe surface of the side not having an image-recording layer of anotherlithographic printing plate precursor were directly brought into contactas shown in FIG. 1. The laminate was packaged with kraft paper linedwith an aluminum foil and fixed with an adhesive tape as shown in FIG.2, whereby a packaged body was manufactured.

Example 2

The image-recording layer coating solution (2) having the compositionshown below was coated on the same support B as in Example 1 with barcoating, dried at 100° C. for 60 seconds in the oven to form animage-recording layer having a dry coating weight of 1.0 g/m².Subsequently, the protective layer coating solution (1) having thecomposition shown below was coated on the above image-recording layerwith wire bar coating and dried at 120° C. for 60 seconds in the oven,whereby lithographic printing plate precursor (2) with a protectivelayer having a dry coating weight of 0.20 g/m² was obtained. The centralline average roughness (Ra) of the surface of the lithographic printingplate precursor having the protective layer measured with a needlehaving a diameter of 2 μm was 0.28 μm, and the surface roughness of theside opposite to the image-recording layer was 0.25 μm. The obtainedlithographic printing plate precursors were made a packaged bodyaccording to the same manner as in Example 1.

Image-Recording Layer Coating Solution (2):

  Binder polymer (1) 0.162 g Polymerization initiator (2) shown below0.100 g Infrared absorber (1) 0.030 g Polymerizable compound, AronixM-215 0.385 g (manufactured by Toa Gosei Co., Ltd.) Fluorine surfactant(1) 0.044 g Methyl ethyl ketone 1.091 g 1-Methyl-2-propanol 8.609 gWater 2.425 g Microcapsules (1) 2.640 g

Protective Layer Coating Solution (1):

Inorganic layered compound dispersion (1)  1.5 g Polyvinyl alcohol PVA105 0.06 g (degree of saponification: 98.5 mol %, degree ofpolymerization: 500, manufactured by Kuraray Co., Ltd.)Vinylpyrrolidone-vinyl acetate copolymer 0.01 g LUVITEC VA64W(copolymerization ratio: 6/4, manufactured by ISP Co.) Surfactant,EMALEX 710 0.01 g (manufactured by Nihon Emulsion Co.) Ion exchangewater  6.0 g

Example 3

Lithographic printing plate precursor (3) was manufactured in the samemanner as in Example 2, except that the dry coating weight of theprotective layer was changed from 0.20 g/m² to 1.0 g/m². The centralline average roughness (Ra) of the surface of the lithographic printingplate precursor having the protective layer measured with a needlehaving a diameter of 2 nm was 0.20 nm, and the surface roughness of theside opposite to the image-recording layer was 0.25 nm. The obtainedlithographic printing plate precursors were made a packaged bodyaccording to the same manner as in Example 1.

Example 4

Lithographic printing plate precursor (4) was manufactured in the samemanner as in Example 2, except that inorganic layered compounddispersion (1) used in the protective layer coating solution was changedto inorganic layered compound dispersion (2). The central line averageroughness (Ra) of the surface of the lithographic printing plateprecursor having the protective layer measured with a needle having adiameter of 2 μm was 0.28 μm, and the surface roughness of the sideopposite to the image-recording layer was 0.25 μm. The obtainedlithographic printing plate precursors were made a packaged bodyaccording to the same manner as in Example 1.

Preparation of Inorganic Layered Compound Dispersion (2):

To 193.6 g of ion exchange water was added 6.4 g of Bengel (refinedmontmorillonite, manufactured by HOJUN), and the mixture was dispersedwith a homogenizer until the average particle size (a laser scatteringmethod) reached 2.1 μm.

Example 5

Lithographic printing plate precursor (5) was manufactured in the samemanner as in Example 2, except that inorganic layered compounddispersion (1) used in the protective layer coating solution was changedto inorganic layered compound dispersion (3). The central line averageroughness (Ra) of the surface of the lithographic printing plateprecursor having the protective layer measured with a needle having adiameter of 2 μm was 0.27 μm, and the surface roughness of the sideopposite to the image-recording layer was 0.25 μm. The obtainedlithographic printing plate precursors were made a packaged bodyaccording to the same manner as in Example 1.

Preparation of Inorganic Layered Compound Dispersion (3):

To 193.6 g of ion exchange water was added 6.4 g of Bengel W-100(anionic polymer complex refined montmorillonite, manufactured by HOJUNCo., Ltd.), and the mixture was dispersed with a homogenizer until theaverage particle size (a laser scattering method) reached 1.8 μm.

Example 6

Lithographic printing plate precursor (6) was manufactured in the samemanner as in Example 2, except that inorganic layered compounddispersion (1) used in the protective layer coating solution was changedto inorganic layered compound dispersion (4). The central line averageroughness (Ra) of the surface of the lithographic printing plateprecursor having the protective layer measured with a needle having adiameter of 2 μm was 0.23 μm, and the surface roughness of the sideopposite to the image-recording layer was 0.25 μm. The obtainedlithographic printing plate precursors were made a packaged bodyaccording to the same manner as in Example 1.

Preparation of Inorganic Layered Compound Dispersion (4):

To 193.6 g of ion exchange water was added 6.4 g of Kunipia G (sodiummontmorillonite, manufactured by Kunimine Industries Co., Ltd.), and themixture was dispersed with a homogenizer until the average particle size(a laser scattering method) reached 1.8 μm.

Example 7

Lithographic printing plate precursor (7) was manufactured in the samemanner as in Example 2, except that the dry coating weight of theprotective layer was changed from 0.20 g/m² to 2.4 g/m². The centralline average roughness (Ra) of the surface of the lithographic printingplate precursor having the protective layer measured with a needlehaving a diameter of 2 μm was 0.20 μm, and the surface roughness of theside opposite to the image-recording layer was 0.25 μm. The obtainedlithographic printing plate precursors were made a packaged bodyaccording to the same manner as in Example 1.

Example 8

Lithographic printing plate precursor (8) was manufactured in the samemanner as in Example 1, except that nylon brushes planted with hairshaving a hair diameter of 0.3 mm used in manufacturing the support waschanged to nylon brushes planted with hairs having a hair diameter of0.72 mm. The central line average roughness (Ra) of the surface of thelithographic printing plate precursor having the protective layermeasured with a needle having a diameter of 2 μm was 0.60 μm, and thesurface roughness of the side opposite to the image-recording layer was0.25 μm. The obtained lithographic printing plate precursors were made apackaged body according to the same manner as in Example 1.

Comparative Example 1

Lithographic printing plate precursor (R1) was manufactured in the samemanner as in Example 3, except that inorganic layered compounddispersion (1) used in the protective layer coating solution wasexcluded. The central line average roughness (Ra) of the surface of thelithographic printing plate precursor having the protective layermeasured with a needle having a diameter of 2 μm was 0.15 μm, and thesurface roughness of the side opposite to the image-recording layer was0.25 μm. The obtained lithographic printing plate precursors were made apackaged body according to the same manner as in Example 1.

Comparative Example 2

Lithographic printing plate precursor (R2) was manufactured in the samemanner as in Example 1, except that inorganic particle dispersion (1)shown below was used in place of inorganic layered compound dispersion(1) used in image-recording layer coating solution (1). The central lineaverage roughness (Ra) of the surface of the lithographic printing plateprecursor having the protective layer measured with a needle having adiameter of 2 μm was 2.0 μm, and the surface roughness of the sideopposite to the image-recording layer was 0.25 μm. The obtainedlithographic printing plate precursors were made a packaged bodyaccording to the same manner as in Example 1.

Preparation of Inorganic Particle Dispersion (1):

To 193.6 g of ion exchange water was added 6.4 g of Mizukasil P-802(silica gel, manufactured by Mizusawa Industrial Chemicals, Ltd.), andthe mixture was dispersed with a homogenizer until the average particlesize (a laser scattering method) reached 2.4 μm.

Comparative Example 3

A packaged body was manufactured in the same manner as in Example 2,except that interleaving sheets were inserted between every sheet of 50sheets of the lithographic printing plate precursors (that is, theimage-recording layer was in touch with the interleaf directly). Theinterleaf used was made from 100 mass % of broad leaved bleached kraftpulp, weighing 30 g/m², density of 0.8 g/cm³, water content of 4.5 mass%, Beck's smoothness of about 500 sec, and pH of 5.5.

Exposure of Lithographic Printing Plate Precursor and Printing Method:

Each of the obtained lithographic printing plate precursors wassubjected to exposure with Trendsetter 3244VX (manufactured by CreoProducts Incorporated) loading a water-cooling type 40 W infraredsemiconductor laser on the conditions of output of 9 W, external drumrotating speed of 210 rpm, and resolution of 2,400 dpi. The exposedprinting plate precursor was mounted on SOR-M cylinder (manufactured byHeidelberg Japan K.K.) without performing development. A fountainsolution (CDS 803 diluted 50 times with city water, manufactured byTokyo Printing Ink Mfg. Co., Ltd.) and TRANS-G (N) Sumi Ink(manufactured by Dainippon Ink and Chemicals Inc.) were supplied as thefountain solution and ink, and printing was begun at a printing speed of6,000 sheets per hour.

The number of the sheets of printing paper required up to the time whenthe on-press development of the unexposed area of the image-recordinglayer finished and the ink did not transfer to printing paper wascounted, and the number of sheets was taken as the on-pressdevelopability. Printed substance free from staining on the non-imagearea could be obtained within 100 sheets with every lithographicprinting plate precursor.

Evaluation of Packaged Body:

With the packaged bodies prepared in Examples and Comparative Examples,adhesion, scratch resistance, aging stability and press life wereevaluated as follows. The results obtained of the evaluations are shownTable 2 below. The contents of each packaged bodies in Examples andComparative Examples are shown in Table 1 below.

(1) Adhesion

The packaged body was preserved under atmosphere of 35° C. 85% RH for 1month and then unfolded. The adhesion of the lithographic printing plateprecursors to each other was evaluated. The case capable of separatingthe lithographic printing plate precursors was graded o, and the case ofincapable of separation due to adhesion of the lithographic printingplate precursors was graded x.

(2) Scratch Resistance

The packaged body was subjected to vibration test according to JIS Z0232 on the conditions of the peak acceleration ±7.35 m/s² and vibrationtime of 60 min. After that, the lithographic printing plate precursorwas subjected to exposure and on-press development as above. The100^(th) printed matter was taken out, and an abnormal place where theink did not adhere to the image area, or an abnormal place where the inkadhered to the non-image area was visually observed. In the case of freeof abnormality was graded o, and the case with abnormality was graded x.

(3) Aging Stability

The packaged body was preserved under atmosphere of 35° C. 85% RH for 1month and then unfolded. After that, the lithographic printing plateprecursor was subjected to exposure and on-press development as above.The 100^(th) printed matter was taken out, and the presence or absenceof an abnormal place where the ink adhered to the non-image area wasvisually observed. In the case of free of abnormality was graded o, andthe case with abnormality was graded x

(4) Press Life

The packaged body was preserved under atmosphere of 35° C. 85% RH for 1month and then unfolded. After that, the lithographic printing plateprecursor was subjected to exposure and on-press development as above,and printing was further continued. With the increase of the number ofprinted papers, the abrasion of the image-recording layer graduallyproceeds, ink receptivity lowers, and the density of ink on the printingpaper starts to decrease. Press life was evaluated by the number of theprinted matters at the time when the ink density (reflection density)reduced by 0.1 from the starting time of printing.

TABLE 1 Contents of packaged bodies in Examples and Comparative ExamplesNo. of Coating Lithographic Weight of Printing Image Protective SurfaceExample Plate Recording Layer Roughness No. Precursor Layer ProtectiveLayer (g/m2) (μm) Interleaf Example 1 (1) Coating Soln. (1) None 0.4 Notused Example 2 (2) Coating Soln. (2) Containing inorganic layered 0.20.28 Not used compound dispersion (1) Example 3 (3) Coating Soln. (2)Containing inorganic layered 1 0.2 Not used compound dispersion (1)Example 4 (4) Coating Soln. (2) Containing inorganic layered 0.2 0.28Not used compound dispersion (2) Example 5 (5) Coating Soln. (2)Containing inorganic layered 0.2 0.27 Not used compound dispersion (3)Example 6 (6) Coating Soln. (2) Containing inorganic layered 0.2 0.23Not used compound dispersion (4) Example 7 (7) Coating Soln. (2)Containing inorganic layered 2.4 0.2 Not used compound dispersion (1)Example 8 (8) Coating Soln. (1) None 0.6 Not used Comparative ComparisonCoating Soln. (2) Not containing inorganic 1 0.15 Not used Example 1 (1)layered compound dispersion Comparative Comparison Coating Soln. (1)None 2 Not used Example 2 (2) added with filler Comparative (2) CoatingSoln. (2) Containing inorganic layered 0.2 0.28 Used Example 3 compounddispersion (1)

TABLE 2 Results of Evaluation Press Life Example Scratch Aging (numberof No. Adhesion Resistance Stability sheets) Example 1 ∘ ∘ ∘ 20,000Example 2 ∘ ∘ ∘ 30,000 Example 3 ∘ ∘ ∘ 25,000 Example 4 ∘ ∘ ∘ 30,000Example 5 ∘ ∘ ∘ 30,000 Example 6 ∘ ∘ ∘ 25,000 Example 7 ∘ ∘ ∘ 15,000Example 8 ∘ ∘ ∘ 15,000 Comparative x x x 1,000 Example 1 Comparative ∘ ∘x 2,000 Example 2 Comparative ∘ ∘ x 30,000 Example 3

It can be seen from the results of the above evaluation that thepackaged bodies in the invention not using interleaving sheets are freefrom the failures such as adhesion and scratch, good in aging stability,and press life can be well maintained.

Example 9

The image-recording layer coating solution (3) having the compositionshown below was coated on support A with bar coating, dried at 120° C.for 60 seconds in the oven to form an image-recording layer having a drycoating weight of 2.0 g/m². Subsequently, the protective layer coatingsolution (2) having the composition shown below was coated on the aboveimage-recording layer with wire bar coating in a dry coating weight of0.3 g/m², and dried at 120° C. for 60 seconds in the same manner,whereby lithographic printing plate precursor (9) was obtained.

Image-Recording Layer Coating Solution (3):

  Polymerizable compound  3.74 mass parts (urethane monomer UA-306H,manufactured by Kyoeisha Chemical Co.,Ltd.) Polymerizable compound  0.78mass parts (acrylic monomer SR-355, manufactured by Nippon Kayaku Co.,Ltd.) Binder polymer (2) shown below  3.53 mass parts Polymerizationinitiator (1)  0.42 mass parts Infrared absorber (2) shown below  0.09mass parts n-Propanol 72.95 mass parts Ion exchange water 18.24 massparts

Protective Layer Coating Solution (2):

Inorganic layered compound dispersion (5) 8.0 g shown below Polyvinylalcohol PVA 110 1.3 g (degree of saponification: 98.5 mol %,manufactured by Kuraray Co., Ltd.) Sodium 2-ethylhexylsulfosuccinate 0.3g Water 133 g 

To 368 g of water was added 32 g of synthetic mica Somasif ME-100(aspect ratio: 1,000 or more, manufactured by CO—OP CHEMICAL CO., LTD.),and the mixture was dispersed with a homogenizer until the averageparticle size (a laser scattering method) reached 0.5 nm.

(2) Exposure and Printing:

Each of the obtained lithographic printing plate precursors wassubjected to exposure with Trendsetter 3244VX (manufactured by CreoProducts Incorporated) loading a water-cooling type 40 W infraredsemiconductor laser on the conditions of output of 10 W, external drumrotating speed of 150 rpm, and resolution of 2,400 dpi. The exposedprinting plate precursor was mounted on SOR-M cylinder (manufactured byHeidelberg Japan K.K.) without performing development. A fountainsolution (EU-3 (an etching solution manufactured by Fuji Photo Film Co.,Ltd.)/water/isopropyl alcohol=1/89/10 (by volume)) and TRANS-G (N) SumiInk (manufactured by Dainippon Ink and Chemicals Inc.) were supplied asthe fountain solution and ink, and printing was begun at a printingspeed of 6,000 sheets per hour. The number of the sheets of printingpaper required up to the time when the on-press development of theunexposed area of the image-recording layer finished and the ink did nottransfer to printing paper was counted, and the number of sheets wastaken as the on-press developability. The results obtained are shown inTable 4.

In the case of negative lithographic printing plate precursor, thedegree of hardening of an image-recording layer (photosensitive layer)is low and press life is low when the exposure amount is small, on theother hand the degree of hardening is high and press life is high whenthe exposure amount is large. Press life was evaluated by continuingprinting. With the increase of the number of printed papers, theabrasion of the image-recording layer gradually proceeds, and inkreceptivity lowers, so that the density of ink on the printing paperdecreases. Press life was evaluated by the number of the printed mattersat the time when the ink density (reflection density) reduced by 0.1from the starting time of printing. The results obtained are shown inTable 4 below.

Examples 10 to 14 and Comparative Example 4

Lithographic printing plate precursors (10) to (14) and comparativelithographic printing plate precursor (R4) were manufactured in the samemanner as in Example 9, except that the binder polymer were changed asshown in Table 3 below, and on-press developability and press life wereevaluated. The results obtained are shown in Table 4.

TABLE 3 Binder Polymer Ex. 9 

Ex. 10

Ex. 11

Ex. 12

Ex. 13

Ex. 14

Comp. Ex. 4

Comparative Example 5

The image-recording layer coating solution (3) shown above was coated onthe same support as in Example 9 with bar coating, dried at 120° C. for60 seconds in the oven to form an image-recording layer having a drycoating weight of 2.0 g/m². Subsequently, the protective layer coatingsolution (3) having the composition shown below was coated on the aboveimage-recording layer with wire bar coating in a dry coating weight of 2g/m², and dried at 120° C. for 60 seconds in the same manner, wherebycomparative lithographic printing plate precursor (R5) was obtained.On-press developability and press life were evaluated in the same manneras in Example 1. The results obtained are shown in Table 4.

Protective Layer Coating Solution (3):

Polyvinyl alcohol PVA 110 5.26 g (degree of saponification: 98.5 mol %,manufactured by Kuraray Co., Ltd.) Polyvinyl imidazole 0.93 g Ionexchange water 93.81 g 

Comparative Example 6

The image-recording layer coating solution (3) shown above was coated onthe same support as in Example 9 with bar coating, dried at 120° C. for60 seconds in the oven to form an image-recording layer having a drycoating weight of 2.0 g/m², whereby comparative lithographic printingplate precursor (R6) was obtained. A protective layer was not provided.With the obtained lithographic printing plate precursor, on-pressdevelopability and press life were evaluated in the same manner as inExample 9. The results of evaluation are shown in Table 4.

TABLE 4 On-Press Press Life Developability Example No. (number of sheet)(number of sheet) Example 9 20,000 30 Example 10 15,000 30 Example 1120,000 30 Example 12 25,000 40 Example 13 25,000 40 Example 14 10,000 60Comparative 5,000 150 Example 4 Comparative 0 — Example 5 (imageformation failure) Comparative 1,000 30 Example 6

From the results in Table 4, it can be seen that the lithographicprinting plate precursors in the invention are excellent in on-pressdevelopability and press life.

Example 15

Lithographic printing plate precursor (15) was manufactured in the samemanner as in Example 9, except that the image-recording layer coatingsolution (4) shown below was used in place of the image-recording layercoating solution (3) in Example 9, and evaluations were performed in thesame manner as in Example 9. The number of press life was 20,000 sheetsand the number of on-press developability was 30 sheets.

Image-recording layer coating solution (4) was prepared by mixing andstirring the following photosensitive solution (1) and microgel solution(1) just before coating.

Photosensitive Solution (1):

Binder polymer (2) in Example 9 0.162 g Polymerization initiator inExample 9  0.1 g Infrared absorber (2) in Example 9 0.020 gPolymerizable compound, Aronix M-215 0.385 g (manufactured by Toa GoseiCo., Ltd.) Fluorine surfactant (1) 0.044 g Methyl ethyl ketone 1.091 g1-Methoxy-2-propanol 8.609 g

Microgel Solution (1):

Microgel (1) synthesized as follows 2.640 g Distilled water 2.425 g

Synthesis of Microgel (1):

As the oil phase component, 10 g of the addition product oftrimethylolpropane and xylene diisocyanate (Takenate D-110N,manufactured by Mitsui Takeda Chemicals Inc.), 3.15 g of pentaerythritoltriacrylate (SR444, manufactured by Nippon Kayaku Co., Ltd.), and 0.1 gof Pionin A-41C (manufactured by Takemoto Oil & Fat) were dissolved in17 g of ethyl acetaate. As the aqueous phase component, 40 g of a 4 mass% aqueous solution of PVA-205 was prepared. The oil phase component andthe aqueous phase component were mixed, and emulsified with ahomogenizer at 12,000 rpm for 10 minutes. The obtained emulsifiedproduct was added to 25 g of distilled water, stirred at roomtemperature for 30 minutes, and then stirred at 50° C. for 3 hours. Theconcentration of the solids content of the obtained microgel solutionwas diluted with distilled water to reach 15 mass %. The averageparticle size of the obtained microgel solution was 0.2 μm.

Examples 16 to 26 and Comparative Examples 7 to 13

The image-recording layer coating solution shown below was coated onsupport C with bar coating, dried at 100° C. for 60 seconds in the ovento form an image-recording layer having a dry coating weight of 1.0g/m². Subsequently, the protective layer coating solution (4) or (5)having the composition shown below was coated on the aboveimage-recording layer with bar coating, and dried at 125° C. for 75seconds in the oven to form a protective layer, whereby lithographicprinting plate precursors (16) to (26) and comparative lithographicprinting plate precursors (R7) to (R13) were obtained.

The image-recording layer coating solutions were prepared by mixing andstirring the following photosensitive solutions ((2) to (12) and (r1) to(r5)) and microcapsule solution (2) just before coating.

Photosensitive Solution (2) to (12) and (r1) to (r5):

Binder polymer (1) 0.147 g Radical generator (the compound shown in X gTable 5) Infrared absorber (the compound shown in Y g Table 5) Additivefor discoloration (the compound Z g shown in Table 5) Polymerizablecompound (Aronix M-215 0.350 g manufactured by Toa Gosei Co., Ltd.)Fluorine surfactant (1) 0.040 g Methyl ethyl ketone 0.991 g1-Methoxy-2-propanol 7.816 g

Microcapsule Solution (1):

Microcapsule (1) shown above 2.397 g Water 2.202 g

Protective Layer Coating Solution (4):

Polyvinyl alcohol PVA 105 2.24 g (degree of saponification: 98.5 mol %,degree of polymerization: 500, a 6 mass % aqueous dispersion,manufactured by Kuraray Co., Ltd.) Vinyl acetate-vinylpyrrolidonecopolymer 0.0073 g  Luviskol VA64W, a 50 mass % aqueous solution,manufactured by BASF Japan) Polyvinyl pyrrolidone (30K, manufactured by0.0053 g  Wako Pure Chemical Industries) Surfactant (EMALEX 10, a 1 mass% aqueous 2.15 g solution, manufactured by Kao Corporation) Flakysynthetic mica (MEB3L, 3.75 g average particle size: 1 to 5 μmΦ, a 3.4mass % water dispersion, manufactured by UNICOO) Distilled water 10.60g 

Protective Layer Coating Solution (5):

Polyvinyl alcohol PVA 105  2.24 g (degree of saponification: 98.5 mol %,degree of polymerization: 500, a 6 mass % aqueous solution, manufacturedby Kuraray Co., Ltd.) Vinyl acetate-vinylpyrrolidone copolymer 0.0073 gLuviskol VA64W, a 50 mass % aqueous solution, manufactured by BASFJapan) Polyvinyl pyrrolidone (30K, manufactured by 0.0053 g Wako PureChemical Industries) Surfactant (EMALEX 10, a 1 mass % aqueous  2.15 gsolution, manufactured by Kao Corporation) Distilled water  10.60 g

(2) Exposure and Printing:

Each of the obtained lithographic printing plate precursors wassubjected to exposure with Trendsetter 3244VX (manufactured by CreoProducts Incorporated) loading a water-cooling type 40 W infraredsemiconductor laser on the conditions of output of 9 W, external drumrotating speed of 210 rpm, and resolution of 2,400 dpi, so that theexposure image contained a fine line chart. After exposure, thevisibility (plate-detecting property) of the fine line chart wasvisually evaluated.

The exposed printing plate precursor was mounted on SOR-M cylinder(manufactured by Heidelberg Japan K.K.) without performing development.A fountain solution (EU-3 (an etching solution manufactured by FujiPhoto Film Co., Ltd.)/water/isopropyl alcohol=1/89/10 (by volume)) andTRANS-G (N) Sumi Ink (manufactured by Dainippon Ink and Chemicals Inc.)were supplied as the fountain solution and ink, and printing wasperformed at a printing speed of 6,000 sheets per hour. At this time,the number of the sheets required up to the time when the ink did nottransfer to the unexposed area (non-image area) of the image-recordinglayer (on-press developability) was evaluated.

When the number of printed papers increases by further continuingprinting, the abrasion of the image-recording layer gradually proceeds,and ink receptivity lowers, so that the density of ink on the printingpaper decreases. Press life was evaluated by the number of the printedmatters at the time when the ink density (reflection density) reduced by0.1 from the starting time of printing. The results obtained are shownin Table 5 below.

From the results in Table 5, it can be seen that Examples 16 to 26 thatused the lithographic printing plate precursors and the lithographicprinting method of the invention are excellent in the visibility of theprinting plates after exposure and on-press developability, little inloss paper, and showed good press life.

TABLE 5 Image-Recording Layer Litho- Infrared Radical graphic AbsorberGenerator Additive Printing Photo- Addition Addition Addition Ex. Platesensitive Amount Amount Amount No. Precursor Layer Structure X (g)Structure Y (g) Structure Z (g) Ex. 16 (16) (2) (1) 0.034 (4) 0.125 NoneEx. 17. (17) (3) (1) 0.034 (5) 0.119 None Ex. 18. (18) (4) (1) 0.034 (6)0.119 None Ex. 19 (19) (5) (1) 0.034 (7) 0.159 None Ex. 20 (20) (6) (1)0.034 (7) 0.159 None (1) 0.086 Ex. 21 (21) (7) (1) 0.034 (7) 0.159 None(2) 0.157 Ex. 22 (22) (8) (1) 0.034 (7) 0.159 None (3) 0.141 Ex. 23 (23)(9) (3) 0.036 (7) 0.159 None Ex. 24 (24) (10)  (4) 0.036 (7) 0.159 NoneEx. 25 (25) (11)  (5) 0.036 (7) 0.159 None Ex. 26 (26) (12)  (6) 0.027(7) 0.159 None Comp. (R7)  (r1) (1) 0.034 (6) 0.086 (1) 0.090 Ex. 7Comp. (R8)  (r2) (1) 0.034 (6) 0.086 (2) 0.090 Ex. 8 Comp. (R9)  (r3)(1) 0.034 (6) 0.119 (3) 0.050 Ex. 9 Comp. (R10) (r4) (1) 0.034 (6) 0.119(4) 0.050 Ex. 10 Comp. (R11) (r5) (1) 0.034 (6) 0.086 (5) 0.040 Ex. 11Comp. (R12) (8) (1) 0.034 (7) 0.159 None Ex. 12 (3) 0.141 Comp. (R13)(8) (1) 0.034 (7) 0.159 None Ex. 13 (3) 0.141 Variation in Absorbance ofProtective Infrared Absorber Performance Layer Wave- Amount of Plate Ex.Coating length Variation in Detecting On-Press Press No. Solution (nm)Absorbance Property Developability Life Ex. 16 (4) 645 Increase Good 3011,000 by 0.09 Ex. 17. (4) 650 Increase Good 60 9,000 by 0.08 Ex. 18.(4) 650 Increase Very 30 12,000 by 0.12 good Ex. 19 (4) 650 IncreaseGood 30 10,000 by 0.11 Ex. 20 (4) 650 Increase Very 50 8,000 by 0.13good Ex. 21 (4) 650 Increase Good 70 10,000 by 0.10 Ex. 22 (4) 650Increase Very 50 17,000 by 0.14 good Ex. 23 (4) 640 Increase Good 4011,000 by 0.08 Ex. 24 (4) 680 Increase Very 40 10,000 by 0.11 good Ex.25 (4) 555 Increase Almost 60 11,000 by 0.06 good Ex. 26 (4) 650Increase Almost 60 9,000 by 0.06 good Comp. (4) Good 200 2,000 Ex. 7Comp. (4) Almost 300 3,000 Ex. 8 good Comp. (4) Good 200 5,000 Ex. 9Comp. (4) Very 250 4,000 Ex. 10 good Comp. (4) Bad 500 8,000 Ex. 11Comp. (5) 650 Increase Very 500 12,000 Ex. 12 by 0.09 good Comp. (5) 650Increase Very 60 2,000 Ex. 13 by 0.09 good

Example 27

A lithographic printing plate precursor was manufactured in the samemanner as in Example 16, except that the following microgel solution (2)was used in place of microcapsule solution (2), and evaluations wereperformed in the same manner as in Example 16.

The lithographic printing plate precursor showed good plate-detectingproperty, and the number of on-press developability was 30 sheets andthe number of press life was 12,000 sheets. The absorbance of theinfrared absorber at 645 nm increased by 0.10 by exposure.

Microgel Solution (2):

Microgel (2) synthesized as follows 2.397 g Distilled water 2.202 g

Synthesis of Microgel (2):

As the oil phase component, 10 g of the addition product oftrimethylolpropane and xylene diisocyanate (Takenate D-110N,manufactured by Mitsui Takeda Chemicals Inc.), 3.15 g of pentaerythritoltriacrylate (SR444, manufactured by Nippon Kayaku Co., Ltd.), and 0.1 gof Pionin A-41C (manufactured by Takemoto Oil & Fat) were dissolved in17 g of ethyl acetaate. As the aqueous phase component, 40 g of a 4 mass% aqueous solution of PVA-205 was prepared. The oil phase component andthe aqueous phase component were mixed, and emulsified with ahomogenizer at 12,000 rpm for 10 minutes. The obtained emulsifiedproduct was added to 25 g of distilled water, stirred at roomtemperature for 30 minutes, and then stirred at 50° C. for 3 hours. Theconcentration of the solids content of the obtained microgel solutionwas diluted with distilled water to reach 15 mass %. The averageparticle size of the obtained microgel solution was 0.2 nm.

The invention can provide a packaged body of lithographic printing plateprecursors dispensing with a development process free of interleavingsheets, by which the lithographic printing plate precursors can beprevented from the generation of adhesion and scratches, andpreservation stability and press life can be maintained well. Theinvention can further provide a lithographic printing plate precursorexcellent in on-press developability and press life. The invention canstill further provide an on-press development type or non-processingtype (non-development type) lithographic printing plate precursor thatis excellent in the visibility of a printing plate after exposure,little in loss paper, and having good press life. The invention canfurther provide a lithographic printing method including on-pressdevelopment with these lithographic printing plate precursors.

The entire disclosure of each and every foreign patent application fromwhich the benefit of foreign priority has been claimed in the presentapplication is incorporated herein by reference, as if fully set forth.

1. A lithographic printing plate precursor comprising: a support; animage-recording layer comprising (A) an actinic ray absorber, (B) apolymerization initiator and (D) a binder polymer, and theimage-recording layer is capable of being removed by at least one of aprinting ink and a fountain solution; and a protective layer comprisingan inorganic layered compound, in this order, wherein the binder polymerhas an ethylene oxide group.
 2. The lithographic printing plateprecursor according to claim 1, wherein the inorganic layered compoundhas an aspect ratio of 10 or more.
 3. The lithographic printing plateprecursor according to claim 1, wherein the binder polymer has from 2 to120 repeating units comprising an ethylene oxide group.
 4. Thelithographic printing plate precursor according to claim 1, wherein thebinder polymer has from 6 to 60 repeating units comprising an ethyleneoxide group.
 5. The lithographic printing plate precursor according toclaim 1, wherein the binder polymer is water-insoluble.
 6. Thelithographic printing plate precursor according to claim 1, wherein theimage-recording layer comprises discontinuous particles.
 7. Thelithographic printing plate precursor according to claim 1, wherein thebinder polymer is polymer particles dispersed in the image-recordinglayer.
 8. The lithographic printing plate precursor according to claim1, wherein the image-recording layer comprises at least one ofmicrocapsules and microgels.
 9. The lithographic printing plateprecursor according to claim 1, wherein the protective layer has a massof from 0.02 to 1 g/m².
 10. A lithographic printing method comprising:imagewise exposing a lithographic printing plate precursor according toclaim 1 by irradiation with an actinic ray; removing an area notirradiated with an actinic ray of the image-recording layer by feedingat least one of a printing ink and a fountain solution; and performingprinting.
 11. A lithographic printing plate precursor comprising: asupport; an image-recording layer capable of imaging by an infraredlaser exposure; and a protective layer, in this order, wherein thelithographic printing plate precursor is capable of printing by beingmounted on a printing press without a development process after an imagerecording or by an image recording after being mounted on a printingpress, and wherein the image-recording layer comprises (E) an infraredabsorber and (F) an iodonium salt and does not substantially comprise acompound other than an infrared absorber (E) which changes a color ofthe compound by interacting with at least one of an acid, a base and aradical, and the protective layer comprises an inorganic layeredcompound.
 12. The lithographic printing plate precursor according toclaim 11, wherein an absorbance at any wavelength of from 400 to 700 nmof an infrared absorber (E) in an exposed area changes by at least 0.05or more by an infrared laser exposure as compared with an absorbance ofan infrared absorber (E) in an unexposed area.
 13. The lithographicprinting plate precursor according to claim 11, wherein an absorbance atany wavelength of from 400 to 700 nm of an infrared absorber (E) in anexposed area becomes greater by at least 0.05 or more by an infraredlaser exposure as compared with an absorbance of an infrared absorber(E) in an unexposed area.
 14. The lithographic printing plate precursoraccording to claim 11, wherein the infrared absorber (E) is a compoundrepresented by formula (D1)

wherein R¹ and R² each independently represents a hydrogen atom or ahydrocarbon group having from 1 to 12 carbon atoms, and R¹ and R² may bebonded to each other to form a cyclic structure; Ar¹ and Ar² eachindependently represents an aromatic hydrocarbon group which may have asubstituent; Y¹ and Y² each independently represents a sulfur atom or adialkylmethylene group having 12 or less carbon atoms; R³ and R⁴ eachindependently represents a hydrocarbon group having 20 or less carbonatoms which may have a substituent; R⁵, R⁶, R⁷ and R⁸ each independentlyrepresents a hydrogen atom or a hydrocarbon group having 12 or lesscarbon atoms; R⁹ and R¹⁰ each independently represents an aromatichydrocarbon group having from 6 to 10 carbon atoms which may have asubstituent, an alkyl group having from 1 to 8 carbon atoms or ahydrogen atom, and R⁹ and R¹⁰ may be bonded to each other to form acyclic structure, and in this case, the cyclic structure may arbitrarilycontain one or more hetero atoms selected from the group consisting of anitrogen atom, an oxygen atom and a sulfur atom; and X⁻ represents acounter anion, provided that when any of R¹ to R⁸ is substituted with asulfo group, X⁻ is not necessary.
 15. The lithographic printing plateprecursor according to claim 11, wherein the image recording layerfurther comprises a sulfonium salt.
 16. The lithographic printing plateprecursor according to claim 11, wherein the image recording layercomprises at least one of microcapsules and microgels.
 17. Alithographic printing method comprising: imagewise exposing alithographic printing plate precursor according to claim 11 with aninfrared laser; removing an unexposed area of an image-recording layerin a state of fitting the lithographic printing plate precursor to acylinder of a printing press, so as to form a lithographic printingplate; and performing printing with the lithographic printing plate.